yeah, the black-box is the best security wise, but totally breaks what GPL stands for. If you want to be fancy I believe there is a loophole that works something like GPL LGPL Closed Source or you could just say fuck it :/
Though I personally I'm no big GPL fan, I honor what it stands for to the end when working with GPL'ed code :/
But if you need help porting the engine to Mac or/and Linux I can probably help you there, though I'm having some time/hardware issues that hopfully will get solved soon (the reason I haven't offered my assistant sooner).
-RisK