I guess the thing that concerns me (not speaking for anyone else) has largely been the (admittedly late) realization that Github can be bought.
I had, for some indiscernible reason, thought of Github as this near-benevolent entity that existed exclusively to facilitate open-source and distribute Octocat stickers. When they were purchased by one of the largest megacorporations on the planet, it pulled-back the curtain, and showed that, no, they are a for-profit business, not a charity.
I shouldn't have thought that way, but I did, and as a result the MS-buying-Github thing has not sat well with me.
I also think GitHub, essentially, positioned themselves that way. However, that, if viewed a bit cynically, could easily be seen as just marketing or PR.
I think the slight difference is that MS does have a history of shitting all over open-source software (Ballmer famously said Linux was cancer years ago). While I'm aware that companies change people all the time, it's unsurprising that some people get a little bit uneasy about them owning the largest distributor of open-source.
I mean, it’s not that difficult to make the case that their support of OSS over the last decade was specifically to buy developers’ goodwill, though I don’t think that’s the case and think GitHub was headed this way anyhow.
But that aside, I don't see how any corporation should be trusted to host such a large percentage of OSS. Whether it's a year from now or 10 years from now, what do you expect to happen when Microsoft's material interests cease to align with supporting OSS? Do you think they will subvert their own interests in the support of some "greater good"? Given the history of how corporations behave, I think that would be very unlikely.
It's dangerous to anthropomorphise corporations (or nations). Yes, corporate culture is sticky but you can more easily change a corporate culture by a radical demographics change both at the base and at the top, and redesigning the incentives.
That goes both ways and it's why you cannot have inherently "good" corporations either (no matter what their positive track record is).
I would be hesitant to describe a single CEO's tenure as enough time.
The honest answer is at best I can forgive their bad behaviour. But I'll never forget it.