Huh?!? I just about creamed myself there.
Embrace. Extend. Extinguish. Once again. 
-40hz
This I worry about. We'll see though.
However, this time around it won't be so obvious. We'll need to be much more alert. -Renegade
Interesting patent verbiage from Microsoft on this (full text
here):
Microsoft Patent Promise for .NET Libraries and Runtime Components
Microsoft Corporation and its affiliates ("Microsoft") promise not to assert
any .NET Patents against you for making, using, selling, offering for sale,
importing, or distributing Covered Code, as part of either a .NET Runtime or
as part of any application designed to run on a .NET Runtime.
If you file, maintain, or voluntarily participate in any claim in a lawsuit
alleging direct or contributory patent infringement by any Covered Code, or
inducement of patent infringement by any Covered Code, then your rights under
this promise will automatically terminate.
This promise is not an assurance that (i) any .NET Patents are valid or
enforceable, or (ii) Covered Code does not infringe patents or other
intellectual property rights of any third party. No rights except those
expressly stated in this promise are granted, waived, or received by
Microsoft, whether by implication, exhaustion, estoppel, or otherwise.
This is a personal promise directly from Microsoft to you, and you agree as a
condition of benefiting from it that no Microsoft rights are received from
suppliers, distributors, or otherwise from any other person in connection with
this promise.
A couple of things:
(1) I don't know what the legal ramifications of "a personal promise" are. But it apparently isn't the same thing as a" contract" or a "guarantee" - otherwise why make such a distinction? Pretty vague if you ask me. Be interesting to see how something like that would play out in court if push came to shove.
(2) If you discover something in .Net that you think is infringing on one of
your patents, it looks like you waived the "personal promise" not to be sued for infringement of Microsoft's claimed patents on .Net
That's a bit of a double-bind that gets Microsoft neatly off the hook either way.
If it does turn out to be genuine, I will be a very happy camper! 
That seems to be more the case with the Windows dev crowd than the Linux developers and maintainers - except for the Mono project, which is generally regarded as a "trojan project."
But time will tell.
I'm sure the in-house biz devs will be happy hearing this since they can now more easily port their proprietary .Net apps over to a less expensive OS. Won't their bean counters and upper management be pleased to hear that!
