Ultimately a court will have to settle this, which may be what the FSF is looking toward. The recent decision calling open source licenses contracts, subject only to the redress due on any other contract, may actually help the FSF in making this argument.
The "model train" decision held that license violations are subject only to money damages, not injunctive relief. Microsoft's deal with Novell, along with subsequent deals made with other Linux distros, seems to go only to the question of injunctive relief.
If the FSF and Microsoft come to legal blows over this issue, however, money damages are precisely what the FSF would be seeking. The claim will be that Microsoft is interfering in a business relationship and should pay.
All this is far from even drawing up legal papers, but it does illustrate a new-found confidence on the part of the FSF in taking on Microsoft over legal issues important to it. With all enormous enterprises now endorsing open source as a concept -- IBM, Sun, Google, etc. this could be an important turning point.