Multiple licensing

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With multiple licensing , users can choose from several software licenses . So a program can e.g. B. be used under an open source license such as the GPL and under a proprietary license. Such a license selection is then also called a dual license system or model . But it is also possible to use several open source licenses, e.g. B. the GPL and a BSD license .

Prominent examples of double licensing in the software sector are Qt , MySQL , Asterisk , Sendmail and Perl (GPL and Artistic License ) .

advantages

With this licensing principle, companies can develop their own applications without having to subject them to the open source license again. On the one hand, it is possible to promote the open source model for the development and distribution of software and, on the other hand, to establish a professional business model in which software licenses can be sold without restrictions. The option of adding proprietary extensions to the software also speaks in favor of multiple licensing.

Furthermore, buyers of software that has been licensed multiple times are not bound by the sometimes very restrictive requirements for distributing software under a free license. The development of free software is promoted without having to rely on donations.

disadvantage

An argument against multiple licensing is that the licensing company could take advantage of the work of external open source developers. In addition, the developing company could reserve the right to stop further development of the open version at some point. However, it is then still possible for anyone else to further develop the last open version, see spin-off (software development) .

It is controversial whether the initiator of an open source project that brings his software onto the market under a dual license can incorporate the further developments of the community into his product in order to sell it under a license other than the GPL.

Small companies generally run the risk of “losing” their open source software projects to large companies.