In response to this recent post, there have been quite a few others and there is a long discussion about it in OS News, as well as other places. Among the comments:

Novell has received those license from microsoft so novell has nothing to fear but other vendors who didnt sign up with the microsoft threats are vunerable.

Novell is pushing mono technology in gnome - since it has the cross-patent license from microsoft.

[...]

On November 2, 2006, Microsoft and Novell announced a joint agreement whereby Microsoft agreed to not sue Novell�€Ã¯Â¿Â½s customers for patent infringement.[9] According to Mono project leader Miguel de Icaza,[10] this agreement extends to Mono but only for Novell developers and customers. http://en.wikipedia.org/wiki/Mono_(software)#Mono_and_Microsoft.E2.80.99s_patents

That last part implies that Microsoft COULD possibly sue people or organizations that use Mono.

So... given the relationship between Microsoft and Novell, and how Novell is the big organization pushing Mono, maybe there IS something to be concerned about. This situation does look suspiciously like Microsoft worming its way into having power in the FOSS world.