stealing GPL code

If you use some GPL code and then don't share your code, is there anyway they can find out?? This is about a turn-based strategy game btw if that matters.

>>1
Yes. Nobody ever chooses willingly to apply the GPL to their project: they are only forced to do so because they depend on another GPL'd project. Maybe someday we will break free from this vicious circle, but in the meantime, don't be the next victim.