GNU General Public License

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Logo of the GPLv3

The GNU General Public License ( GNU GPL or GPL for short ; from English literally for general permission or permission to publish ) is the most widely used software license that grants one to run, study, modify and distribute (copy) the software. Software that grants these freedoms is called free software ; and if the software is copylefted , these rights must be retained when it is passed on (with or without software modification, expansion, or software reuse). Both are the case with the GPL.

The original license was written by Richard Stallman of the Free Software Foundation (FSF) for the GNU project . The FSF recommends the current, third version (GNU GPL v3 ), which was published in 2007.


The GPL can be used by anyone as a license in order to guarantee the freedom of end users. It is the first general-use copyleft license. Copyleft means that changes or derivatives of GPL-licensed works may only be distributed under the same license conditions (i.e. GPL). The GPL thus grants the recipients of a computer program the freedoms of Free Software and uses copyleft to ensure that these freedoms are retained in the event of further distribution, even if the software is changed or expanded. Permissive licenses like the BSD license, on the other hand, do not require copyleft.

Software licensed under GPL may be executed for all purposes (including commercial purposes, and GPL-licensed compilers and editors may also be used as tools for creating proprietary software). In the case of purely private (or internal) use without distribution and without distribution, it may be modified without the source code having to be disclosed (only in the case of distribution or distribution, the source code and any code changes must be made accessible to end users - then copyleft is used Application to ensure that end-user freedoms are preserved). However, software that runs as an application program under a GPL-licensed operating system such as GNU / Linux does not necessarily have to be distributed under GPL or open source. The licensing then only depends on the libraries and software parts used (not on the underlying platform). If, for example, an application program only contains its own software or is combined with open-source software parts that are not subject to strict copyleft (i.e. no GPL parts), then the self-developed software parts do not have to be placed under the GPL or open source (even if the operating system used is licensed under GPL). The source code must be made available to users (under the same license conditions: GPL) only when realizing software that combines new (own) source code parts with GPL parts (and if this software is distributed or distributed). The GNU Lesser General Public License (LGPL) was developed to have a weaker copyleft than GPL: LGPL does not require that your own developed code parts (which LGPL parts use but are independent of them: e.g. only library Call) must be made available under the same license conditions.

Users and companies may charge for the distribution of GPL-licensed works (commercial distribution) or distribute them free of charge. This distinguishes GPL from software licenses, which prohibit commercial distribution. The FSF declares that software that respects freedom must not restrict commercial and commercial use and distribution (including redistribution): The GPL expressly states that GPL works (e.g. free software ) can be sold or redistributed at any price.


The GNU GPL was written in January 1989 by Richard Stallman , founder of the GNU Project .

It was based on a standardization of similar licenses that were used in earlier versions of GNU Emacs , the GNU Debugger and the GNU Compiler Collection . These licenses were specifically tailored to each program, but contained the same provisions as the current GNU GPL. Stallman's goal was to develop a license that could be used on any project. This is how the first version of the GNU General Public License , published in January 1989, came about .

In June 1991 the Free Software Foundation (FSF) published the second version of the GNU GPL (GPL v2 ). The most important change was the Liberty or Death clause (Liberty or Death) in Section 7. This says: If it is not possible to comply with some conditions of the GNU GPL - for example because of a court judgment - it is forbidden to use this license only to meet in the best possible way. In this case, it is no longer possible to distribute the software at all. Paragraph 8 was also added: This allows an author to geographically restrict the validity of the license in order to exclude countries in which the exploitation of the work is restricted by patents or by interfaces protected by copyright. In addition, the second version is compatible with non-US legal systems as it is based on the Berne Convention .

At the same time, on June 2, 1991, a new license with the name GNU Library General Public License (GNU LGPL) with version number 2.0 (GNU LGPL v2.0) was published, which is a relaxed version of the GNU GPL acts. It was introduced because it became clear since 1990 that the GNU GPL was in some cases (mostly for program libraries ) too restrictive (restrictive). The GNU LGPLv2 (June 1991) was originally designed for a few specific libraries. The license implements the model of a weak copyleft, whereby the program libraries under it no longer mean that the programs using them must also be licensed under the same conditions, but further developments of the libraries themselves are still subject to the GNU LGPL. With version 2.1, released in February 1999, the license was renamed the GNU Lesser General Public License , the new name was a suggestion by Georg Greve .

Since its inception, the GPL has been the most widely used free software license. Most of the programs in the GNU project are licensed under the GPL and LGPL, including the GCC compiler collection , the GNU Emacs text editor and the Gnome Desktop. Many other programs by other authors that are not part of the GNU project are also licensed under the GPL. In addition, all LGPL-licensed products are also licensed under the GPL.

The first draft of the third version of the GPL was presented to the public for discussion on January 16, 2006. Three more designs followed. On June 29, 2007, the finished version of GPL 3 was finally published.

When the GPLv3 was published in 2007, Richard Stallman announced that he would not wait so long for the next GPL version ("GPLv4") this time, but would tackle one within the next ten years; However, nothing is known about specific planning.

GPL version 3

On June 29, 2007, 16 years after version 2 was released in 1991, the license was revised with version 3. Some of the biggest and most important changes are:

  1. The GPL is supposed to be a global license. From version 2 onwards it supports internationalization relatively successfully by relying on the minimal principles of the Bern Convention for the Protection of Works of Literature and Art, but it was still too strongly based on the US legal system. For this reason, national legal characteristics should be given more importance without violating the irrevocable basic principles of the GPL.
  2. For Section 3 of the GPL Version 2, which was responsible for the distribution, copying and modification of software , and Section 7, which was authoritative for regulating patents and other legal restrictions , changes should be introduced that reflect the different interests and Combine the viewpoints of all license participants as well as possible.
  3. The GPL is the constitution for the free software movement. First and foremost, therefore, social and political intentions are in the foreground, only then technical and economic ones. An absolute basic principle is the free exchange of knowledge , as well as free access to technical knowledge and means of communication, based on the model of scientific freedom . Developments such as software patents , trusted computing and DRM , which counteract these principles, should be viewed from a socio-political point of view and thus taken into account in the GPL, whereby the stated freedoms must remain unaffected.

The FSF, as the holder of the GPL under the direction of Richard Stallman, coordinated the revision and was advised by Eben Moglen . The desired universality of the GPL 3 inevitably resulted in competing interests. On January 16, 2006, a first preliminary draft was published and put up for discussion in order to achieve the best possible result for future publication.

The GPLv3 has been controversial since the first draft was published. The aspect of tivoisation , which was not considered in the previous version v2 , was controversially discussed in the design phase . The FSF proposal is intended to prevent tivoization in the future, but the Linux kernel initiator Linus Torvalds criticized this approach and took the position that tivoization should remain allowed. Torvalds particularly criticized the first two drafts extremely sharply and still sees no reason to put the Linux kernel under this version of the license. There was also strong criticism from Linspire , Novell , MySQL and others. Some companies - especially MySQL - then changed the license wording of their products from "GPLv2 or later" to "GPLv2 only". Besides the Linux kernel , some other FOSS projects decided not to switch to GPLv3: BusyBox , AdvFS , Blender , and the VLC media player .

Another aspect of discussion was whether the GPLv3 Affero should allow -like requirements, which the so-called ASP -gap in the GPL ( English ASP loophole in the GPL would have) closed. However, after some concerns about the additional administrative effort had been expressed, it was decided to keep the Affero license as a separate license from the GPL.

There was also controversy about the mixability of GPLv2 software with GPLv3 software, which is only possible under the optional or later clause of the GPL. But this was as pure emergency option (of some developers english safeboat clause considered), but not to change as a regular way the license significantly. The existing projects that have licensed their software without the optional clause are also best known of the Linux kernel , which makes them incompatible with GPLv3 software and cannot exchange source code with it. One example is the GNU LibreDWG library , which can no longer be used by LibreCAD and FreeCAD .

After three further drafts, the final version was published on June 29, 2007. As a side effect of the revision, several additional licenses have become GPL-compatible.

The significantly expanded GPLv3 is assessed as essentially incompatible with GPLv2, compatibility between the two licenses is only given via the optional clause this version or later , which is not used by some projects, for example the Linux kernel . In 2011, four years after GPLv3 was released, only 6.5% of all open source projects are GPLv3, while 42.5% are GPLv2 , according to Black Duck Software data . In 2013, six years after the GPLv3 was published, the GPLv2 is still by far the most widely used license, according to Black Duck. In 2011, in connection with this split, other authors noted an increased movement towards permissive licenses , away from copyleft licenses.

Some journalists and developers conclude from the low migration of projects from the old GPLv2 to the newer GPLv3 that there is a division of the community along the boundaries of the two license versions.

Copyleft principle

All programs derived from a work under the GPL may only be distributed by licensees if they are also licensed by them under the terms of the GPL. This only affects licensees, not rights holders. (The copyright holder - that is the author or someone to whom the author has assigned his rights - can also redistribute the work under any other license.) Richard Stallman called this protection process “ copyleft ” - as an allusion to the word copyright . The aim is to ensure the freedom of a program also in the further development of others.

This principle can also be found in other licenses - among others in the GNU licenses ( LGPL , AGPL and GFDL ) and referred to as “Share Alike” in some of the Creative Commons licenses.

Compatibility of licenses with the GNU GPL

Since the GPL guarantees and requires certain freedoms to be maintained for the software recipients (even if the software is subsequently passed on to other recipients, or if the code is changed or parts of code are reused: copyleft); GPL-licensed software parts cannot be combined with software parts whose licenses require that recipients renounce certain freedoms, or demand that freedoms must be withdrawn from other recipients. Such licenses are incompatible with the GNU GPL.

The GNU Project maintains a list of licenses that are compatible with the GNU GPL. These include certain permissive Free Licenses (but not all) that are compatible with the GNU GPL. Permissive licenses, taken by themselves , allow developers and distributors to choose to withdraw certain freedoms from the recipients when they are passed on (hence "permissive"); In any case, such a withdrawal is not absolutely necessary: ​​In the case of a combination with GPL-licensed software code parts, such a withdrawal is not permitted if it would restrict the freedoms granted by the GPL: GPL-licensed software code parts may can only be changed, expanded or combined with other software parts if the combined result still grants all recipients the freedoms of the GPL (the copyleft of the GPL must be preserved).

The FSF also considers copyleft with program libraries to be justified in principle, but grants exceptions for programs for which it has the rights, sometimes for strategic reasons, for example to increase the acceptance of a library. In these cases the Lesser General Public License (LGPL) is recommended by the FSF, which explicitly allows this use without making copyleft demands on the calling program.

Application to a new program

The GPL contains an appendix that describes how to apply the license to a new program. The appendix contains a standard template that includes the name of the program, a brief description of what it does, the year of creation and the name of the author. The template contains a disclaimer warning that the program comes without any guarantee. It licenses the program under the respective GPL version, with the addition "or (at your option) any later version", which also opens the program to the terms of future versions of the GPL. This means that the program is automatically under a new GPL version as soon as the Free Software Foundation publishes one. This enables the license change to a new version of the GPL and prevents compatibility problems between different versions. Some projects also use the template for GPL version 2 without the addition, since they do not agree with GPLv3. The template also contains a note on where to find a copy of the GPL if a copy is not included with the program.

There is no central registry for GPL-licensed programs, but the FSF and UNESCO operate a directory without any claim to completeness.

Legal position


With a modernization of German copyright law developed between 2000 and 2002, it should be anchored in law that an author cannot in any case do without appropriate remuneration. Theoretically, this would have resulted in legal uncertainty for dealers who sell free software, as programmers might have subsequently been able to demand a portion of the proceeds, which would have opened up opportunities for abuse. With the addition of the so-called Linux clause to the draft law , the GPL (and similar licenses that “grant a simple right of use for everyone free of charge”, cf. Section 32 (3) sentence 3 UrhG ) were placed on a secure legal basis.

In a written judgment dated May 19, 2004 (Az. 21 O 6123/04 ), the Munich District Court I confirmed an injunction prohibiting a company from distributing Netfilter without complying with the GPL. This was the first time that the GPL played a significant role in a German court case. The court assessed the defendant's activities as a violation of some of the terms of the GPL and thus as a copyright infringement. This corresponded exactly to the forecasts that Eben Moglen of the FSF had previously made for such cases. The basis of the decision was the German translation of the GPL, which the court checked to some extent for its validity as terms and conditions. For some clauses, complicated legal constructions or interpretations were necessary in order to achieve the admissibility under German law. The opposing party had not attacked the admissibility of the terms of the GPL, but only denied that it was the correct defendant at all.

On September 6, 2006, the GPL was successfully part of the proceedings against D-Link at the Frankfurt am Main regional court (Ref .: 2-6 O 224/06 ).

On October 4, 2006, the validity of the GPL was confirmed in a further judgment. A representative of the programmers of three GPL-licensed auxiliary programs for starting an operating system kernel went to court after a warning against a company that had used the programs in its firmware without disclosing their source code and without having enclosed the GPL. The claims in the injunction request were partially not met, which is why the court ruled that the company had violated the plaintiff's copyright and thus named the origin and the buyer of the firmware as well as the court and warning costs and the costs for the effort to establish the legal violation must. The defendants had tried to defend themselves with a whole range of usual arguments, including the invalidity of the GPL due to anti-competitive factors, the prohibition on the use of evidence due to copyright infringement in the determination of the infringement (i.e. unauthorized decompilation of the firmware - the plaintiff had only observed the boot process), and the exhaustion principle and the lack of the right to file a lawsuit, since in the context of open source development only co-authorship can be assumed and the consent of the other authors is required for the lawsuit. However, the court rejected all of these arguments.

United States

On March 21, 2006, the American Daniel Wallace failed with a lawsuit in the district court in the US state of Indiana against the FSF . He had taken the position that the GPL was ineffective. Through the availability of free software copies, it enforces a price agreement between the various providers, which is a violation of the Sherman Antitrust Act . Judge John Daniel Tinder disagreed with this view and noted that it would be difficult to determine an infringement of antitrust law if the interests of the plaintiff diverged from those of the consumers. Lawsuits against Red Hat , Novell and IBM were also dismissed.

Miscellaneous to the legal situation

To protect the rights of GPL authors and to be able to take action against violations, Harald Welte founded the project in 2004 . has already successfully taken to court several times on behalf of programmers. In a number of other cases, an out-of-court settlement was reached.


The copyright of the license text itself lies with the Free Software Foundation (FSF). This allows copying and distribution of the license in the head of the license, but prohibits the modification of the license text. This ensures that the rights and obligations guaranteed by the GPL cannot be changed by changing the license text. This also prevents different incompatible versions of the GPL from being created. The FSF allows the creation of new licenses on the basis of the GPL, as long as they have a new name of their own, do not contain the preamble of the GPL and do not refer to the GNU project. This originally happened, for example, with the GNU Affero General Public License before it was adopted by the FSF.

The GPL does not dispute the copyright laws of the country concerned, but accepts them and uses them to enforce the rights and obligations described. A work licensed under GPL is not in the public domain . Unless expressly stated otherwise, the author retains the copyright to the work and can take legal action against it in the event of non-compliance with the license conditions.

Distribution history

On the open source hoster SourceForge , around 70% of the software was licensed under the GPL in July 2006, in May 2016 only around 59% (87,692 projects with GPLv2 license, 14,880 projects with GPLv3 license, a total of 175,081 projects).

In 2008, 67% of the 3489 projects on the BerliOS developer platform (2334 projects) were under the GPL. The developer platform was shut down in 2014.

The Open Source Resource Center , managed by Black Duck Software, indicated the spread of GPLv2 among open source projects with 32.65% and that of GPLv3 with 11.62% in 2012. According to an undated list of the most widely used open source licenses, more recent values ​​are only 20% for GPLv2 and 8% for GPLv3.

The company Palamida operates a "GPL3-Watchlist", according to which about 2946 of the 10,086 registered projects are registered under the GPLv3, but the selection of projects is not representative. The numbers from the Open Source License Resource Center suggest that in July 2008 around three to four percent of GPL projects were using the third version. It does not take into account that the standard text of the Free Software Foundation for the release of a program under the GPL provides that use is also permitted under any later version of the GPL. This means that programs licensed under GPL 2 that use the standard text can also be used under GPLv3 and future versions.

For 2015, GitHub reports that only around 20% of the projects registered there contain license information. Of these, just under 13% use the GPLv2, almost 9% the GPLv3 and a good 1% the AGPLv3.


Criticism of the GPL mainly consists of criticism of the strong copyleft and criticism of the principle of free software . For example, Microsoft's former CEO Steve Ballmer referred to Linux in 2001 as a cancer because of the effects of the GPL. In 2001, Craig Mundie , Microsoft senior vice president , publicly described the GPL as viral. Stephen Davidson of the World Intellectual Property Organization used the term viral for the copyleft properties of the GPL in a guide to the open source model (in which he generally draws rather cautious conclusions) . Others later criticized the GPL's viral properties as well.

Supporters of free software have also criticized the GPL for its limited compatibility with other licenses (and between the GPL variants) as well as its complex license text.


See also: Literature on Free and Open Source Software

Web links

Explanations, analyzes, etc.

Individual evidence

  1. are z. For example, if certain GPL-licensed software parts are used in completely different / new software, this software must, if passed on ... grant the recipient the full freedom of the GPL (under a GPL-compatible license); except when so few / few GPL software parts are used (snippet with a few small lines) that "fair use" would apply
    see Compatibility of Licenses with the GNU GPL ,
    Ref: Source Code in Documentation ,
    Ref: GPL Fair Use ,
    Ref: Linking with GPL ,
    Ref: GPL Static vs Dynamic
  2. How to choose a license for your own work. Free Software Foundation , accessed September 10, 2014 .
  3. GPL FAQ: Does using the GPL for a program make it GNU Software?
  4. GPL FAQ: Use GPL Tools to develop non-free programs
  5. GPL FAQ: GPL require source posted to public , Unreleased modifications , Internal Distribution
  6. a b GPL FAQ: Port program to GNU / Linux (also applies under GPL v2 )
  7. Application programs for Linux (p. 18) ( altern. ); No “derivative work” - clear case groups (p. 65) ; Book " The GPL - commented and explained " (Published: ifrOSS, 2005)
  8. license terms ; Linux device drivers, 2nd edition. (English: 1 , 2 ); Note: the English "3rd edition" states somewhat more cautiously that the use of binary ( "binary form only" - that is, without source code) "loadable kernel device driver modules under Linux" is not clear (but so far tolerated): Link
  9. ^ Embedded Linux and Copyright Law ; Dave Beal and Michael Barr
  10. so if z. For example, if only LGPL libraries, LGPL software parts and parts with permissive software licenses are used (not GPL), only the LGPL parts need to be open-source and changeable - any self-developed software parts are then not subject to this requirement (themselves if the operating system used is licensed under GPL, such as GNU / Linux)
  11. GPL FAQ: use GPL commercially
  12. Commercial software ; not to be confused with proprietary (
  13. Sell ​​free software. Free Software Foundation, accessed January 21, 2013 .
  14. GPL FAQ: Sell ​​copies of the program for money , Distribute commercially
  15. Presentation by Richard Stallman (April 21, 2006, second international GPLv3 conference, in Porto Alegre)
  16. GNU Library General Public License, version 2.0. Free Software Foundation, accessed October 30, 2018 .
  17. ^ Georg CF Greve: Activities, Miscellaneous ( Memento of December 17, 2007 in the Internet Archive ) on the private homepage, May 10, 2002.
  18. ^ Speech on the publication of the GPLv3 "We won't wait more than a decade, this time."
  19. Heise Open: Conciliatory tones about the new draft
  20. ^ Heise Open: Dispute over the GPL
  21. MySQL changes license to avoid GPLv3 ( Memento of February 6, 2007 in the Internet Archive ) on Computer business review online (January 4, 2007).
  22. ^ Mark: The Curse of Open Source License Proliferation. (No longer available online.), May 8, 2008, archived from the original on December 8, 2015 ; Retrieved on November 30, 2015 : “ Currently the decision to move from GPL v2 to GPL v3 is being hotly debated by many open source projects. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  23. Corbet: Busy busy busybox., October 1, 2006, accessed on November 21, 2015 : " Since BusyBox can be found in so many embedded systems, it finds itself at the core of the GPLv3 anti-DRM debate. [...] The real outcomes, however, are this: BusyBox will be GPLv2 only starting with the next release. It is generally accepted that stripping out the "or any later version" is legally defensible, and that the merging of other GPLv2-only code will force that issue in any case "
  24. ^ Rob Landley: Re: Move GPLv2 vs v3 fun ..., September 9, 2006, accessed on November 21, 2015 : “ Don't invent a straw man argument please. I consider licensing BusyBox under GPLv3 to be useless, unnecessary, overcomplicated, and confusing, and in addition to that it has actual downsides. 1) Useless: We're never dropping GPLv2. "
  25. Press release concerning the release of the AdvFS source code
  26. Alexandre Prokoudine: What's up with DWG adoption in free software?, January 26, 2012, accessed December 5, 2015 : " [Blender's Toni Roosendaal:]" Blender is also still "GPLv2 or later". For the time being we stick to that, moving to GPL 3 has no evident benefits I know of. " "
  27. Rémi Denis-Courmont: VLC media player to remain under GNU GPL version 2., accessed on November 21, 2015 : " In 2001, VLC was released under the OSI-approved GNU General Public version 2, with the commonly- offered option to use "any later version" thereof (though there was not any such later version at the time). Following the release by the Free Software Foundation (FSF) of the new version 3 of its GNU General Public License (GPL) on the 29th of June 2007, contributors to the VLC media player, and other software projects hosted at, debated the possibility of updating the licensing terms for future version of the VLC media player and other hosted projects, to version 3 of the GPL. [...] There is strong concern that these new additional requirements might not match the industrial and economic reality of our time, especially in the market of consumer electronics. It is our belief that changing our licensing terms to GPL version 3 would currently not be in the best interest of our community as a whole. Consequently, we plan to keep distributing future versions of VLC media player under the terms of the GPL version 2. "
  28. Michael Tiemann: GNU Affero GPL version 3 and the "ASP loophole". OSI , June 7, 2007, accessed August 19, 2013 .
  29. List of free software licenses on the FSF website : “ We recommend that developers consider using the GNU AGPL for any software which will commonly be run over a network ”.
  30. Why did you decide to write the GNU Affero GPLv3 as a separate license? on (English).
  31. a b Rob Landley: CELF 2013 Toybox talk -, accessed on August 21, 2013 (English): " GPLv3 broke" the "GPL into incompatible forks that can't share code. [...] FSF expected universal compliance, but hijacked lifeboat clause when boat wasn't sinking. [...] "
  32. a b Linus Torvalds: COPYING., accessed on August 13, 2013 : “ Also note that the only valid version of the GPL as far as the kernel is concerned is _this_ particular version of the license (ie v2, not v2.2 or v3.x or whatever ), unless explicitly otherwise stated. "
  33. a b Frequently Asked Questions about the GNU Licenses - Is GPLv3 compatible with GPLv2?, accessed on April 13, 2011 (English): “ No. Some of the requirements in GPLv3, such as the requirement to provide Installation Information, do not exist in GPLv2. As a result, the licenses are not compatible: if you tried to combine code released under both these licenses, you would violate section 6 of GPLv2. "
  34. Michael Larabel: FSF Wastes Away Another "High Priority" Project. Phoronix , January 24, 2013, accessed on August 22, 2013 (English): “ Both LibreCAD and FreeCAD both want to use LibreDWG and have patches available for supporting the DWG file format library, but can't integrate them. The programs have dependencies on the popular GPLv2 license while the Free Software Foundation will only let LibreDWG be licensed for GPLv3 use, not GPLv2. "
  36. A Quick Guide to GPLv3 .
  37. a b Bruce Byfield: 7 Reasons Why Free Software Is Losing Influence: Page 2. , November 22, 2011, accessed on August 23, 2013 : “ At the time, the decision seemed sensible in the face of a deadlock. But now, GPLv2 is used for 42.5% of free software, and GPLv3 for less than 6.5%, according to Black Duck Software. "
  38. Top 20 licenses. (No longer available online.) Black Duck Software , August 23, 2013, archived from the original on July 19, 2016 ; accessed on August 23, 2013 : " 1st GNU General Public License (GPL) 2.0 33%, 2nd Apache License 13%, 3rd GNU General Public License (GPL) 3.0 12% " Info: The archive link was automatically inserted and still Not checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  39. ^ Matthew Aslett: The trend towards permissive licensing. (No longer available online.), June 6, 2011, archived from the original on May 11, 2013 ; Retrieved on August 23, 2013 : " [...] the GPL family of licenses has fallen to 61% today from 70% [...] In comparison the number of Apache licensed projects grew 46% over the past two years, while the number of MIT licensed projects grew 152%. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  40. ^ Brian Proffitt: GPL, copyleft use declining faster than ever - Data suggests a sharper rate of decline, which raises the question: why? IT world , December 16, 2011, accessed on August 23, 2013 .
  41. Richard Stallman :Copyleft: Pragmatic Idealism (English)
  42. What does it mean to say that two licenses are “compatible”? GPL FAQ (
  43. ^ Various licenses and comments
  44. Original BSD license and others are libertarian as well as permissive licenses, but incompatible with the GNU GPL
  45. Boost Software License , Modified BSD License , Expat License (usually referred to as "MIT License") , Apache License, Version 2.0 etc. are licenses that grant freedom as well as permissive licenses and are compatible with the GNU GPL
  46. in the sense of a software change, expansion or reuse
  49. bill of the SPD and the Open Group, BT printed matter 14/6433 (PDF; 124 kB)
  50. Holger Bleich:German court confirms the effectiveness of the GPL, Message on heise online from July 23, 2004.
  51. ^ Judgment of the Munich Regional Court 1
  52. Oliver Diedrich: GPL prevails in German courts., September 10, 2006, accessed on June 18, 2015 .
  53. LG Frankfurt am Main .: GPL is effective ( memento of the original from October 17, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , LG Frankfurt, 2–6 O 224/06, archive link ( Memento of the original from June 27, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / @1@ 2Template: Webachiv / IABot /
  54. Andreas Wilkens:Richter rejects cartel lawsuit against GPLon heise online , March 21, 2006.
  55. Another lawsuit against GPL due to alleged obstacle to competition rejectedon heise online , May 22, 2006.
  56. Heise Open article
  57. Download Free Open Source Software - In: Retrieved May 25, 2016 .
  58. BerliOS: Projects according to license. Archived from the original on February 6, 2007 ; accessed on October 6, 2016 .
  59. Open Source License Data. (No longer available online.) In: Open Source Resource Center. Black Duck Software, archived from the original on January 13, 2013 ; accessed on December 6, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  60. Top 20 Open Source Licenses. Black Duck Software, accessed October 6, 2016 .
  61. Ben Balter: Open source license usage on GitHub, accessed October 6, 2016 .
  62. heise online - Microsoft boss Ballmer describes Linux as a cancerous tumor
  63. ^ " Speech Transcript - Craig Mundie, The New York University Stern School of Business ", Prepared Text of Remarks by Craig Mundie , Microsoft Senior Vice President, The Commercial Software Model The New York University Stern School of Business May 3, 2001
  64. heise online - WIPO Guide to Open Source warns of "sleepless nights"
  65. Nikolai Bezroukov : Comparative merits of GPL, BSD and Artistic licenses (Critique of Viral Nature of GPL v.2 - or In Defense of Dual Licensing Idea). 2001, archived from the original on December 22, 2001 ; Retrieved on September 22, 2018 (English): "Viral property stimulates proliferation of licenses and contributes to the" GPL-enforced nightmare "- a situation when many other licenses are logically incompatible with the GPL and make life unnecessary difficult for developers working in the Linux environment (KDE is a good example here, Python is a less known example). "
  66. ^ New Media Rights: Open Source Licensing Guide. California Western School of Law , September 12, 2008, accessed November 28, 2015 : “ The GPL license is 'viral,' meaning any derivative work you create containing even the smallest portion of the previously GPL licensed software must also be licensed under the GPL license. "
  67. David Chisnall: The Failure of the GPL. , August 31, 2009, accessed on January 24, 2016 : “ The GPL places additional restrictions on the code, and therefore is incompatible. You can combine APSL, MPL, CDDL, Apache, and BSD-licensed code in the same project easily, but you can only combine one of these with GPLv2 code. Even the Free Software Foundation can't manage to get it right. Version 3 of the LGPL, for example, is incompatible with version 2 of the GPL. This has caused a problem recently for a few GNU library projects that wanted to move to LGPLv3 but were used by other projects that were GPLv2-only. "
  68. ^ Allison Randal: GPLv3, Clarity and Simplicity. May 14, 2007, archived from the original on October 15, 2008 ; accessed on September 22, 2018 (English).