I don't quite remember it the same way.
Microsoft did own and licsene Xenix for quite some time back in the 80's, and somehow they convinced AT&T to integrate certain parts of their Xenix code into the main UNIX release (I think that this was System III at the time), so for a time all UNIX based O/S's used Xenix code, HP-UX, IRIX, Solaris 2.x, and even Commodore UNIX. I can't recall exactly what Xenix code was integrated (I think it was mainly library stuff, although I'm not positive).
So, M$ was getting paid on all UNIX based O/S's, although I don't know exactly how it was done (liscensing usually confuses me anyhow :-D ). UNIX went from AT&T to Novell to somebody else, eventually ending up with SCO (not the same SCO we've now, which is really just Caldera in disguise).
Mid 90s SCO and Microsoft get involved in a lawsuit against one another (I'm not sure who started it, but it went on for quite some time). SCO was paying M$ lots of dough in liscensing for the code from Xenix, which had been replaced, and was now just empty baggage. M$ thought they could force SCO into keeping their source in the UNIX source, and continue to pay royalties. But they went to court, and SCO won. So there hasn't been any Xenix code in SCO's various OS's for about 7 years now.
I love the irony!
The real question in what M$ is going to do with this.
yes I know I spelt licsensing wrong.
Clark