In the source of the html at the Mill, Frigidman admits that the item about the Mill shutdown being ordered by MS is, in fact, a joke. Since Myth is in fact now owned by Take Two, this would make little sense anyway.
From the source code:
The Mill has been shut off in protest due to recent news about Bungie and Microsoft. It goes against every fiber of my being to run a site that will promote and lengthen the life of a company that is now a part of the useless corporation known as Microsoft. I have my principles and I stand by them. Microsoft is a representation of all things bad in the software industry, and supporting them in any way turns my stomach. It was great running this site for the myth community and for Bungie. However, now that the Big Nasty is in charge of Bungie, I cannot bring myself to ever really take care of the site. So instead of just letting it sit and never get updated, I will just shut it down.
Frigid goes on to confirm that he won't let anyone else run the Mill, either, as it contains a financially significant amount of proprietary code and expensive hardware.