So, the news is that Attachmate got Novell, but Microsoft bought, through its newly-formed consortium, Novell's patents. Why would Microsoft want them so badly? Here's my guess.

Microsoft practiced at least one of Novell's patents

A looming lawsuit from Novell was what motivated the inclusion of the patent deal in the interoperability agreement.

Microsoft didn't get a license from Novell

Under the counter, non-license promise? (Actual license would be GPL violation?)

Microsoft needed control over the patents

Deal about to expire; Novell still vulnerable, hostage business-wise, but another owner might not be so nice.

Microsoft couldn't just buy Novell

Anti-trust concerns. Licensing of patents to all downstream software recipients from Novell under GPL, even v2.

Microsoft's solution

Get someone else to buy Novell minus patents.

Microsoft couldn't have got a patent license from Novell in the 2006 agreement that required a change to the GPLv3 draft available ATM: this would have blocked distributing Novell's GPLv2 software.

This probably means Microsoft had a promise from or agreement with Novell to not assert the very patents that Microsoft was reading on. The deal was about to expire, and it might not survive the acquisition. But Microsoft couldn't just buy Novell, for that would be an anti-trust mess, and it couldn't just buy the patents, for that would amount to have granted licenses to practice these patents to all recipients of Novell software that Microsoft redistributed under the GPL.