Are games made with Unity able to be distributed under the GPL?
Thanks
Good question. I’m neither a lawyer nor a GPL expert, but I think that your own source can be made available as GPL, but I don’t think the game itself can be, because the compiled player isn’t open. I’ve been wondering the same thing, because I have a few little games that I’ve wanted to make open-source, but I’m not sure if the nature of the development environment is compatible.
It’s sort of fuzzy, because you can write programs that are based on closed-source libraries and make them GPL, but I’m not sure that the Unity engine would be considered a library. I suppose it could, but again, I’m not a lawyer. There’s also the monkey-wrench of Unity free versus Unity Pro. Can Unity Pro products be open source? Or just Unity Free? Does it matter? Can something that requires Pro still be compiled in Free, just without those particular features?
Can anyone comment?
I’ve done a little research on this, but it’s still unclear. I sent an email to the Free Software Foundation, and asked for whatever information they can give me. I let them know that there are others that want to go open source with their Unity projects, and I’ll post whatever they send me.
You could definitely release your code under an Open Source license like MIT or BSD that don’t have the restrictions that the GPL does. If you just want to release it open source, use one of those licenses.
That may be the best bet, niosop. They responded by pointing to their FAQ, which confused me even more. 
For the record, here’s where they pointed me:
http://www.gnu.org/licenses/gpl-faq.html#NonFreeTools
If anyone can decipher this in the context of Unity, I would definitely like to know. I guess I’ve just sort of grown up with the GPL, so that was the first one I looked at.
To me the faq is pretty clear, but I have had an IP law course, and have read and studied the GPL in depth.
Basically, the GPL requires that you give away the source to your game, that would include the unity engine… which you neither have the source to or the legal right to distribute the source to under the GPL. So, at the very least, you’ll have to start from scratch and not use any GPL-ed code. That aside… notice the train app… if you write every line of code, only you can enforce the copyright as the original author, so you can technically release code that is in violation of it’s own license as you’re bound on distribution of the code (I have some GPL-ed code that does this, the art is gpl, the code is under a non-gpl license, and the whole is technically undistributable. n.n)* (Consult a lawyer)
Copyright law is complicated. XD Short answer: The faq says no.
Also see:
http://www.gnu.org/licenses/gpl-faq.html#InterpreterIncompat
http://www.gnu.org/licenses/gpl-faq.html#WhoHasThePower
http://www.gnu.org/licenses/gpl-faq.html#OOPLang
If you want something copyleft, you could use the mozilla tri-license. The mozilla license is a file-by-file copyleft. It allows use in commercial programs, but is the closest that I’ve found to copyleft that doesn’t jump all over the place (they have to release the source to any files which contain mozilla licensed code). The tri-license includes the GPL and LGPL as well, and derivative works may select any of the 3 licenses, though need not force you to select the same of the three. IN short, meeeting the terms of a license is sufficient and it’s often best to leave any mozilla tri-licensed file under a mozilla tri-license. If you want to talk more about licenses, let me know. I’m not a lawyer, so am not offering legal advice, but I can help choose a license from the flood.
Edit: When distributing a mozilla tr-licensed binary including unity, you would need to meet either the terms of the mozilla or lesser gnu public licenses to have the legal rights granted therein.