A small nit-pick:
I think it's important to make clear that I believe that everything that Six Apart did was legal. MT is their property, and they can write whatever license agreement they want. They can place any terms and restrictions in it that they want. It's their business to run as they will, and they make their own decisions.
It is true that MT can write whatever license agreement they want. This does not necessarily make those terms legal or enforceable.
Kathy Kinsley's personal blog has even more good comments on this issue as well.