Yes, that was the original contrast, versus the MIT license of the OP. Sure, people will opt to not release code when it contains trade secrets or whatnot, but the thread is about MIT vs GPL, basically.
Anyway, not to play thread police, it just seemed to me that it was veering off into another direction. I'm cranky in the mornings!
Reusing GPL'd code forces developers to in turn release their code; more free licenses don't have this effect.