Here's a blog that should be interesting to watch on shared source at Microsoft:  http://blogs.msdn.com/jasonmatusow/archive/2005/03/09/391124.aspx

My personal opinion on shared source and community projects - I think there's huge potential.  It's tricky to navigate the waters of IP licensing and building community  - but succesful projects help developers, help tool builders understand needs better, add value to the platform for the end users, it's just win-win-win....  For example, lately I downloaded DotNetNuke - as much ASP.NET VB code as I've ever seen in one place before, and because of its bulk and friendly license (no GPL taint), I'm using it as a crash test dummy for the profiler.   Since it comes from the same people who are eventually going to be using our tools, it just seems that much more "real" than testing against IBuySpy or something.  We'll see how it goes.  :)