What is the worst thing MS can reasonably do?
Microsoft's directory of intellectual property
This is where I say I will license a royalty-free license to my essential patents, and in return I expect you to license your essential patents to me on an royalty-free basis.
we will license this to you royalty free
But lets not waste our time on this discussion on the mailing list, forlegal matters, you should get legal counsel. Have your lawyers engage Microsoft on this topic, that is the only way of getting a solid answer.