When making a game with SDL, is one allowed to release it for profit without providing the source? The GPL license seems to state that you cannot release anything that has a "modified source" without providing the source. But the thing is - I haven't actually changed the SDL source, I've merely used it to create something else!

SDL isn't GPL it's LGPL. As long as you dynamically link to the SDL library you don't need to release the source to your own application.

SDL is LGPL. So, as long as you don't change SDL and you dynamically link to it, you don't need to release the code to your game. You would, however, need to give the source to any changes you made to SDL itself, and presumably provide the source in some way to the SDL libraries.

Thanks guys! That was all I really needed to know! :)