title: What would it take to make Windows a POSIX compliant operating system out of the box?
body: <p>The motivation for this question is a far-fetched dream I have where a lot of the excellent software available on *nix platforms could be trivially ported to Windows.  Microsoft has taken a different approach to open source and openness in general recently, so I'd really like to know how viable such a thing would be if Microsoft were so inclined.  Some of the more specific things I'm curious about is if it could be done without breaking backwards compatibility, and perhaps some sort of gauge on the amount of effort that would be involved.  If there were any specific technical examples that would highlight particular difficulties in doing such a thing, that would also be greatly appreciated.</p>