How soon we forget
Here's a short history of much of the SCO and MS Unix mess. It's not guaranteed complete or 100% accurate, but it's mostly right.
Microsoft had Xenix, one of the first Unix variants for x86. It had Unix licenses for developing that. Xenix became, get this, Santa Cruz Operation's Unix. Santa Cruz Operation later became SCO (the first SCO). Microsoft kept a license for some of the code, and they can do whatever they like with it. This might be part of the stuff they paid SCO for, and they might have licensed SCO-developed code written after the sales, too.
SCO also bought certain rights to Unix from Novell which Novell had bought from Unix System Labs (formerly AT&T's Bell Labs division's Unix division). Apparently, the copyrights were not part of what SCO bought. Neither was an unlimited power to sue over rights in Unix, with Novell able to waive (at Novell's discretion) any action SCO brings in regards to Novell's property.
Caldera was largely a Novell spin-off. Several people from Novell started Caldera, and it was a Linux company. It merged with (it was actually the buyer I think) SCO. They were known for a time after the buyout as Caldera, and the Caldera people where largely running the show. Much of what old SCO had bought from Novell was bought on a "conditional fee" -- they only kept it under conditions of the contract. One of those conditions was that control of the company could not change without voiding large swathes of the contract. Novell would have had to approve the changes in ownership and such in order to waive the nullification, and that never happened. So Caldera had even fewer rights than the old SCO did.
Then, Caldera decided to revive the SCO name. They tried to claim they were old SCO, but they were clearly Caldera, purchaser of old SCO, just changing the label on the package. They were actually still distributing Caldera Linux under the GPL after switching business plans to suing IBM for fun and profit.
Microsoft may have been pulling something dirty by buying all those new licenses at that moment, or they may have done a review of their needs in light of SCO's newly litigious nature. They probably did have something dirty to do with BayStar Capital's cash infusion to SCOX, though, and also with the badly mangled reports from the Alexis de Toqueville Institute (ADTI) that tried just too damn hard to support SCO's story in the press.
Now, we're back to SCO being nobody, Novell clearly the Unix system V copyright holder, and Microsoft being told that they bought a bunch of licenses from a company that didn't have the right to sell them except when acting as an agent of Novell. It turns out the agreement wasn't even the 75% Mo mentions, but that SCO would give all 100% to Novell, and Novell would disburse a 5% handling fee of sorts back to SCO. SCO never paid Novell that money, so Microsoft's licenses it bought from SCO were basically a confidence game. It's no wonder it wanted to talk to Novell.
Even if Microsoft had been just trying to prop up SCO for the suit, it couldn't really admit that, so whatever licenses it paid SCO for it would have had to negotiate with Novell over. If MS claimed they needed the licenses, they needed them to be from Novell. Microsoft can't just say that they already paid, because they paid the wrong party. Just like Microsoft people don't care if you buy Windows from Bobby C.D. Burner unless they get their money, Novell's people don't care if what you bought from SCO if they didn't get their money.
So the MS/Novell IP deal does look bad where Linux is concerned, but it was probably going to happen over just Unix, and Linux got tacked onto the order. Novell already owned the Unix copyrights, and hasn't sued anyone for using Linux.
To say Novell <em>can't</em> sue because they distribute Linux is still silly, though, because Caldera Linux was distributed before and even after the filing of the suit against IBM. SCO obviously did sue after and while distributing Linux. I doubt Novell will sue, though. They were mostly sitting on Unix before. They're pretty much just sitting on it now. They have Netware and the have Linux. They have the Netware browsing/sharing/printing services, Zenworks, Groupwise, and Bordermanager that run on both now AFAICT. Novell is a founding member of the Open Invention Network, which promises to allow anyone to use the group's patents so long as those users agree not to assert patents against Linux. I'd say that tit for tat, Novell is still pretty good for Linux for the present.