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I'm rewriting my entire GPLv3 project in a different language to sidestep angry contributors that don't want me to make money on their contributions.

What I want for my project is:

  • people can use it and contribute like GPL,
  • if you want to embed it in some proprietary solution, you pay.

Basically it's an enforced donation to the project for whom intend to make money.

  1. Is there a standardised license that fits my use case?
  2. If not, is there an existing project you know of I can use as a template?
  • You would still need the permission of your angry contributors to change to a dual license. – Glenn Randers-Pehrson Jun 10 '17 at 11:50
  • I don't think so, they don't own the concepts, but just the implementation. Right? – sscarduzio Jun 10 '17 at 13:22
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    But if you translated some code, that would be a "derivative work" and the contributors of the original code would have copyright rights to your translated work. – Glenn Randers-Pehrson Jun 10 '17 at 18:30
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    Whether A is a derivative of B is (in the U.S.) dependent on 2 factors (1) the author's access to original B and (2) A's similarity to original B. You can try to impose clean-room standards on yourself (i.e., don't look at the code while implementing, only look at requirements) but your familiarity with the code may make it impossible for you to completely diminish the access factor. How "similar" two works are for the similarity factor is subjective but can include non-literal aspects (using someone's fictional character in your new book is infringement, even without literal text copying) – apsillers Jun 11 '17 at 2:18
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    That said, your self-description of the new work as "heavily refactored" is encouraging, and may be dissimilar enough to avoid infringement (but a court of law can tell you for sure, if you get sued). The fact that you're using a new language is less important (e.g., translations of natural-language literary works are still derivatives of the original) – apsillers Jun 11 '17 at 2:21
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As there are no "standard commercial" licenses (see also Commercial licence deproliferation attempts), there is also no standard license combination for a OSS+Commercial dual license.

I know of at least one successful project that uses a OSS+Commercial dual license: The Qt project. From their licensing page:

Qt for Application Development is dual-licensed under commercial and open source licenses. The commercial Qt license gives you the full rights to create and distribute software on your own terms without any open source license obligations. With the commercial license you also have access to the official Qt Support and close strategic relationship with The Qt Company to make sure your development goals are met.

Qt for Application Development is also available under GPL and LGPLv3 open source licenses. [...] The Qt open source licensing is ideal for use cases such as open source projects with open source distribution, student/academic purposes, hobby projects, internal research projects without external distribution, or other projects where all (L)GPL obligations can be met.


When using a OSS+Commercial dual license, it is usually best to choose a copyleft license for the OSS side, because that ensures there is no (or less of a) loophole for commercial users to use the product without paying for the commercial license.

  • Good answer. Note that Qt was not proposed under LGPL before it was bought by Oracle, and thus the incentive to buy the commercial license was even greater. – Zimm i48 Jul 19 '17 at 18:38
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With respect to your question about whether there is an existing project that permits dual-licensing as GPL and as commercial:

The "gregbook" contribution to libpng is dual-licensed, GPLv2+ and BSD-like. See the LICENSE file in libpng16's contrib/gregbook directory. "License 1" specifically permits commercial applications.

  • Oh that is an interesting application of double licensing. What I meant though is dual OSS+Commercial. – sscarduzio Jun 10 '17 at 19:00
  • I believe that if you accept it under the BSD-like license you can use it in a commercial app and relicense it commercially, so long as you abide by the requirement to keep the BSD copyright notice intact. The LICENSE says, "Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:..." – Glenn Randers-Pehrson Jun 10 '17 at 19:25

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