Hi all, I was curious about the legality of mixing Creative Commons and GPL licenses in games. Since warzone2100 was one game I knew that did this, I mentioned it as an example to the FSF licensing address. I thought you might be interested in the response, see the attached message.
-- bye, pabs http://bonedaddy.net/pabs3/
--- Begin Message ---Paul, Thanks for the link to warzone2100. I downloaded the source tarball and perused their website for more information. Since I'm not a lawyer I can only give general guidance about the issues involved. First, the CC-BY-SA license is not compatible with the GPL: https://www.gnu.org/licenses/license-list.html#ccbysa . This is because each is a copyleft. The GPL requires you to release derivatives under the GPL, and the CC-*-SA license(s) require you to use the same license on derivatives. Both can't be true at the same time. If you create a derivative work which combines one work licensed to you under the GPL, and another work under CC-BY-SA, you cannot convey the combination; the GPL will require you to convey the combination under the terms of the GPL, and the CC-BY-SA license will require you to convey the combination under the terms of CC-BY-SA. As far as I know, a work licensed to you under CC-BY-SA 3.0 cannot be distributed by you under the terms of the GPL, any version; that work (or any derivative) can only be distributed by you under the terms of the CC-BY-SA 3.0 license. In the WZ2100 distribution from their web site, I found two PNG files are licensed under CC-BY-SA. It may be possible to contact the author "B.V. Edwards" to see if (s)he would also release the works under the GPL, or under a GPL-compatible license. Also, at least one US court has held that a game can be considered a derivative work of the game engine, see Micro Star v. Formgen, 154 F.3d 1107 (9th. Cir. 1998). The determination of what makes a work a derivative is a legal analysis, so I can't give you guidance on how that plays out for WZ2100; it may turn out that games based on the WZ2100 are derivatives of the engine and therefore must also be released under the terms of the GPL. This may be the intent of the WZ2100 authors; if so, it seems their intent would be protected under the reasoning of the court in the Micro Star case (the reasoning upheld the game author's requirement that third party mods be released "solely for free"). In that case anyone releasing a game based on the WZ2100 would have to convey it (including all of its data) to any third party under the terms of the GPL. Alternately, the WZ2100 authors may choose to allow games to be released under any license. If that is their intent, it would be made clear if they were to release the engine under the GPL with an exception like the GCC runtime exception (https://www.gnu.org/licenses/gcc-exception-faq.html) or the exception included with GNU flex or bison (https://www.gnu.org/software/bison/manual/html_node/Conditions.html). Such an exception should be drafted with the help of legal counsel so it correctly reflects the intent of the author(s). Only the author(s) may make such an exception. If there have been many contributions since the initial release, it may be difficult for the project coordinators to contact all the authors necessary. I hope this helps! -- Thank you for your interest in free software! I am not a lawyer and the above is not legal advice. I am a volunteer. The opinions expressed above do not constitute an official response from the Free Software Foundation. Luigi Bai FSF Associate Member Volunteer, [email protected]
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