CSIRO wifi patent case. A wireless communication technique was patented by the CSIRO and was incorporated into the standard for 802.11a and 802.11g. Earlier this year, over a dozen companies which made use of these techniques, most using their own implementation, reached a settlement with the CSIRO for about $1 billion over unpaid royalties. The companies included Hewlett-Packard, Asus, Intel, Dell, Toshiba, Netgear, D-Link, Belkin, SMC, Accton, 3Com, Buffalo Technologies, Microsoft, and Nintendo, and now the CSIRO are considering other targets (see the link above).
Now the difference here is that the CSIRO made clear from the start that if their technology was included in a standard then people who implemented it would have to pay royalties. In Microsoft's case, they are encouraging use of their tech while saying "don't worry guys, we won't sue.."
With their history, why should anyone believe them?
Halloween docs are just one publicly known example of MS discussing targeting linux. Ever heard of "embrace, extend, extinguish"?
One 'gem' from those docs (written in 1998) is this quote (emphasis mine):
Now re-read that last line, recall that this is taken from a confidential internal Microsoft memo, and tell me again why anyone should trust patented tech that Microsoft 'gives' the community? If you would like to see the context, see the full document linked above.The Linux community is very willing to copy features from other OS's if it will serve their needs. Consequently, there is the very real long term threat that as MS expends the development dollars to create a bevy of new features in NT, Linux will simply cherry pick the best features an [sic] incorporate them into their codebase.
The effects of patents and copyright in combatting Linux remains to be investigated.
Given all this, I think the FSF's statement is quite conservative. I'd be advising people to avoid mono like the plague.