Cannot be emphasized enough. They can get you for copying code but not for reimplementing functionality if you understood how it was implemented.

You'd probably have to write new code; but you could port the algorithms, which are the distillation of their trading expertise. That'd boost you several years ahead in domain knowledge—and, as GS pointed out, you'd also know how GS was going to trade, which would help you predict market movements.

I suspect the latter wouldn't actually be all that accurate, though, since all those split-second decisions are going to be highly dependent on how fast everything runs, which means your GS emulator can't make the same decisions unless you port everything exactly.

You can't use Facebook at GS... E-mail should work but might get suspicious.