> the latter like they'd subtly degrade access from non MS platforms until people wished Google had bought it and shut it down.
Maybe I'm too nice to them, but that doesn't seem like Microsoft's modus operandi anymore. These days they're all about getting people to buy more CPU cycles from Azure, rather than trying to seriously pursue Windows platform lock-in (which is a lost cause and they know it).
I imagine if Microsoft did buy GitHub, they'd have all kinds of offers like "get automated tests and CI to your Azure machines every time you push", or allowing you to host the repo on your own Azure VMs but still use the GitHub interface, stuff like that. They'd probably keep the free GitHub mostly as it is, with some nagging to upsell premium Azure stuff but nothing worse than that.
As for Google, I agree that they tend to get easily distracted and drop things, but I would hope that GitHub is popular enough (both inside and outside Google) that there would be serious pressure not to let it die on the vine. Contrast with abandonware like Wave and Google+ which never got enough mindshare that anyone felt like really fighting for it.
