That's shades of SCO and I don't like it one bit.
It's the carrot at the end of the FUD. "If you buy our stuff, you'll be safe from someone suing."
"What's that, still going to use Unix? Well you'd better at least buy from Novell, as they've signed an agreement protecting you from being sued."
It's not "shades of SCO", it's the other side of the same coin.
Since I've not heard of this happening I'm inclined to believe this is a hollow offer.
Conspiracy-theorists could probably find something interesting in the fact that in general Microsoft seems to be mostly left alone by patent trolls.