Microsoft sells Closed Source and wants the people to use Windows. I don't think they care if the 3rd party software is open source or not, as long as it's running on Windows.
In german magazines there's a Microsoft advert that says something like "Company xy has chosen Windows AND has not chosen Linux" followed by a craplist of lies about system stability etc., that says it all.
I guess the fact that MS is committed to interoperability says something about it being willing to jointly work with open source software vendors to ensure end-users do not suffer due to conflicting standards/specifications. It is a step in the right direction. View it both ways: stuff works with vista/xp as well as stuff works with *NIX. But interoperability acc. 2 MS goes even beyond the OS.
Sorry, but microsoft following standards does only happen if their very own specifications are declared as standard. In visual studio they don't even manage today to completely follow ANSI C99. This should be old enough that even someone at microsoft could have read and implemented this standard...
Sorry, what I think of this is, that it is nothing more than the normal marketing stuff "oh yeah, we will be the good ones, we will help everyone, ...". So far microsoft had to be forced to open at least some things, and those were not really open either (cf NDAs). And what I heard so far about the so called open licenses microsoft created is that you are allowed to read the code but not to change/improve it. This is IMO just a joke and *not* open source software since open source does for me imply that users are allowed to edit the code with only fair restrictions (like keeping those changes open, too).
"Keep your friends close, and your enemies closer..."
I think they're taking that to heart, if you want MY not so humble opinion on the subject. If they think that we can believe that a leopard can change its spots or a tiger it's stripes, especially as fast as this is all happening, heh, they're mistaken.
I'll begin to believe they might be honest and heartfelt about all of this if they let us have access to it and have WRITTEN agreements and not promises to not sue us if we use it and not in "compliant implementations" (which they get to determine...). So far, all I'm seeing is more of the same old plays they've pulled from their playbook for the last 25 or more years now.