Okay, I think I was confusing Mono with Moonlight, which as I see it is not covered by that document. (And Silverlight is an increasingly important piece of the .NET pie.)
Also, given Microsoft's business model and track record, it seems unlikely that .NET is going to hit a steady stable state any time soon, unlike Java which may be stuck at 6 indefinitely. The consequence of this is that Microsoft can break everything, including their promises, anytime they want by bumping the version number and removing the license for the new version. Would it be a good business decision for them? Probably not. But I think this move from Oracle shows that it is a very real possibility, if Microsoft decides they should be taking cues from Oracle (which given Oracle's track record makes a lot of sense, even if this move seems bonkers.)
> since you essentially have to be using a version of Mono that is paid for
What do you mean? The MS-Novel patent deal was done long time ago. Now, there is a better document in place: http://www.microsoft.com/interop/cp/default.mspx - both C# and CLI are covered and no implementation is pointed at. It stops them from suing for "making, using, selling, offering for sale, importing or distributing any implementation" - as long as it's compliant with specs. Stress is on "any implementation" here. That document doesn't mention any specific party and doesn't limit the promise to any specific group as far as I can see.
> Microsoft has intentionally worded their licenses to allow them to sue anyone who isn't paying for their software in the future.
[citation needed]