Licence for a Game

[Ofnuts]

You are utterly mistaken. The GPL only applies to the software and "derivative works" (ie, other software, that you create using parts of the code of the initial software), It doesn't apply to what you produce with it(*). May I suggest that you read the license and in particular its definition of "covered work"?

(*) otherwise all software produced using GPL software (editors, compilers...) would itself be GPL-licensed; right?