I doesn't do anything. By including a GPL-licensed work into your software, you promise not to place any additional restrictions on the result. And it's really

I doesn't do anything. By including a GPL-licensed work into your software, you promise not to place any additional restrictions on the result. And it's really just that. It doesn't force any license on your code. You can still release your individual contributions under a BSD-style license[1]. The one thing you can't do is placing additional restrictions onto your peers. [1] The combined work may be effectively distributable only under GPL-like terms, of course.