This may just be paranoia but if I were competing with Microsoft on something that I'd have private code for hosted on GitHub, I'd be pretty worried right now.
"Oh, but that was way back in the 80s and 90s, and different people run the company now. They're more mature and responsible these days." This is the only argument I've been offered when pointing out Microsoft's very shady history. It doesn't suffice.
[0] http://www.ecis.eu/documents/Finalversion_Consumerchoicepape...
Scanning that, I don't see any mention that this was in any way due to corporate espionage, or weaponizing the customer relationship -- could you point me directly to that part?