Xamarin gets IP -- meaning they don't have to do a clean-room, source-compatible reimplementation of MonoTouch and Mono for Android, and all the risks that go with that -- in exchange for taking on the support of Novell's existing customers. Customers they probably want anyway.
Novell/SUSE gets to get out of the Mono business altogether, which is probably good for them seeing as they laid off the entire engineering staff.
The Mono community gets some clarification about the stewardship of the project. Novell contributed a lot of resources (bug tracker, mailing list and wiki hosting, etc.) and now Xamarin is on the hook for that stuff. It helps clarify the future of the project.
With Xamarin the Mono folks have some skin in the game beyond a paycheck and their own passion. Even if Miguel were to walk away -- something I find unlikely -- there is a business now that depends upon its success and not some neglected division within a rudderless company.
The idea of a safety net for projects like these is just an illusion. There's never a safety net. You've just got to take things as they come and have a backup plan.
That said I think this goes beyond IP for Xamarin. As you said they get the existing customers but they're also available to new customers a few months earlier. Mobile development is growing blazingly fast right now and even a months delay can mean someone decides to go with another product.
With the major financing that companies like Appcelerator have gotten Xamarin needs all the advantages it can get.
Or was it nine lives? Ah, nevermind.
Surely both "partners" are supposed to do something? I don't see Novell lifting a finger here except to abandon their existing Mono customers, get rid of all Mono IP (Mono has IP?) and in every way shape and form wash their hands of the whole thing.
That's good for Xamarin I guess - and kudo's to them if they can make it all work. I'm not sure this is a "win" for Mono - but I guess it's the best of a bad situation.
So the fact that they have signed an agreement that gives Xamarin a perpetual license to all the intellectual property of Mono, MonoTouch, Mono for Android, Mono for Visual Studio, etc, is fantastic for any existing customers which use these products.
This outcome is the best possible outcome given the circumstances.
Mono has IP?
In Mono's case only Novell/Attachmate were able to dual license the runtime libraries, otherwise licensed under LGPL, making it unsuitable for the demands of companies wanting to embed Mono in games (just an example).
Also, MonoTouch and MonoDroid are commercial products and Xamarin had no right to distribute or use in any way any source code or binaries from those projects; meaning they had to start from scratch in producing alternatives which would have been in a gray area, not to mention waisted effort.
You can mix LGPL and proprietary code. I see no reason LGPL libraries would prevent embedding Mono.