Okay, I've read the GPL FAQ, and I'm happy. Specifically:
*Modified versions*
Any modified version is bound by the GPL. This means it can be distributed *under the GPL*, i.e. for free and must make source code available.
*Charging*
Even if someone chooses to charge a fee for it, or a derivative work, anyone who purchases that copy may a) distribute that same version FREE b) request, and distribute the source of that version. Effectively, the GPL renders the sale of versions worthless, as any purchasers can then redistribute the same thing for free! So while charging for copies is not ruled out, they won't make much money out of it!
*Creating a non-GPL version*
Essentially, only the copyright holders can choose to distribute a non-free version of the software. I suggest we all claim joint copyright to each module of code. We can, or someone else can, *by mutual consent from all copyright holders*, choose to create a non-free version. i.e. if we collectively decide to take the code and make a commercial game from it, provided we *all* agree, we can. However, anyone could still gain access to the original GPL version if they so wish, so it'd have to be sufficiently different to justify someone buying that new version. (I'm not suggesting we want to do this, but it's not precluded in the agreement...)
Hope that answers everyone's key questions - it does mine!
*Modified versions*
Any modified version is bound by the GPL. This means it can be distributed *under the GPL*, i.e. for free and must make source code available.
*Charging*
Even if someone chooses to charge a fee for it, or a derivative work, anyone who purchases that copy may a) distribute that same version FREE b) request, and distribute the source of that version. Effectively, the GPL renders the sale of versions worthless, as any purchasers can then redistribute the same thing for free! So while charging for copies is not ruled out, they won't make much money out of it!
*Creating a non-GPL version*
Essentially, only the copyright holders can choose to distribute a non-free version of the software. I suggest we all claim joint copyright to each module of code. We can, or someone else can, *by mutual consent from all copyright holders*, choose to create a non-free version. i.e. if we collectively decide to take the code and make a commercial game from it, provided we *all* agree, we can. However, anyone could still gain access to the original GPL version if they so wish, so it'd have to be sufficiently different to justify someone buying that new version. (I'm not suggesting we want to do this, but it's not precluded in the agreement...)
Hope that answers everyone's key questions - it does mine!