I asked a similar question in another thread, and posted my understanding of the MS-PL:
http://forums.xna.com/forums/t/25200.aspx
I understand that I can distribute an XNA game using the MS-PL license, as long as I distribute it using the same license.
But then again, this website refuses to answer legal questions, and won't give a straight answer, or verify whether my interpretation is correct or not.
IMO, I think it's ridiculous that Microsoft refuses to answer the simple question: "Can I sell my game?" and forcing hobbyists to talk to a lawyer.
Why not say "yes" or "no" or at least "yes, but... blah blah blah"
It reminds me of students in class or colleagues at work who refuse to answer a question as simply as possible, claiming that the only way to answer the question is a very complicated way, so they won't answer the question at all.
Why provide all these wonderful tools and documentation, but neglect to answer the most important final question? What hobbyist will go seek a lawyer as their first option?
I welcome a civilized response to my post, if you disagree with me. (Better yet, please respond if you DO agree with me! :) )