Don't forget Scott Hanselman... I don't think this all would have been possible without any of these persons though. They all deserve some respects.. Even the ones who aren't always visible or the ones who already left Microsoft ( Eg. Phil Haack has made the switch to Github probably because of his opensource work in Microsoft)

They started opensource within Microsoft under Ballmer, so he deserves some respect to. But i'm sure Nadella is making more room for improvement and betting more "all-in"

I just know some people at Microsoft use *nix tools all the time, Asp.Net MVC took over some awesome RoR features, they integrated NodeJS, LocalDB is the alternative for SQLLite and etc...

Microsoft does everything it can to integrate good features and they won't go away anytime soon. They also have the best compatibility in any programming language i know (with .Net) to be a safe bet for businesses...

Hell, even VB6 still works (any Windows Server and a RDP connection) and that has been released in 1998 => 16 years ago!

Policy is made at the top. I can't imagine this happening under Ballmer, though I agree with you that others (Miguel for one) have a lot to do with this.