- It allows them to peek into any private repo on GH right from their own office. All major players host code there, likely a lot of them in private repos too. Microsoft has a large trackrecord of 'me too' products (i.e. the ones released after the original from another company is successful) and corporate espionage isn't something that's just happening in the movies. This too could make things very profitable
- Developer relations across private repos could increase the value of linkedin profiles which in turn could make that more valuable.
But that's about what I could come up with. I seriously don't understand why one would spent $2B on github if it hosts your OSS stuff. Also, to make sure VSTS become more successful with an integration doesn't make sense to me: GH isn't the most profitable service out there and was losing money. Hell it might even go belly up sooner or later and VSTS would look to be a better alternative.
That sounds incredibly unlikely if not borderline ridiculous.
Allows logically, not legally though I'd expect.
I imagine, in my paranoia, the first thing MS will do is change the T&Cs.