MS has a desktop monopoly, now they refuse to sell their CDM to other people operating in that space. Is that kosher or not?
It's kosher as long as anybody else can make a competing CDM that supports Windows and other platforms and sell it to VOD providers. Let me draw an analogy: Microsoft has a desktop monopoly and refuses to sell Halo 2 for other desktop operating systems. Is that kosher? Yes, because anybody else can sell a competing first-person shooter.
The real issue is that GNU/Linux lacks the infrastructure to support a CDM acceptable to the movie studios. To the developers of Linux and X.Org X11, "DRM" means direct rendering manager, not digital restrictions management. I haven't really seen any way to turn off cleartext digital outputs and keep debuggers and hypervisors from teeing the decrypted video to a file.