This is a very interesting move that, on the face of it, seems very positive. PowerShell is not that great and there are plentiful better alternatives available for *nix systems already, so I doubt that it will have much impact in the existing community, but it should make it easier for administrators of Windows to deal with Linux and Apple machines by leveraging what they already know.

As always, I find it hard to trust Microsoft, though. I'm wondering what benefit they are seeking here. It would be nice to think that they have realized how much better it is for everyone to open source code: they get developers for free, less buggy software, better security, etc, plus a load of good will, without giving up anything crucial. I'm pretty sure no one ever bought Windows for PowerShell, so it makes no difference one way or the other to their bottom line, a win-win situation. But their past behaviour makes me suspect an ulterior motive. Are there extra benefits when it runs under Windows? Does it make it easier to treat Windows as a hub for managing other machines rather than vice versa? I'm not a naturally suspicious person, but Microsoft have done bad things too often for me to trust them. Combined with their recent integration of Ubuntu and open-sourcing of .net I think the most obvious motive is a stragegy to embrace and conquer. In essence, they are making it easier to move from Linux/MacOS to Windows, just a little at a time. It's not crazy, it's not particularly evil, as far as I can tell. At least, not yet. It could even backfire, giving people a taste of the alternatives and encouraging them to leave. But, assuming the eventual target is the usual lock-in (once people join the Microsoft ecosystem the company has multiple fiendish means of keeping them in it), it will be interesting to see how this plays out.