I would think that having the update server hardcoded into the application might be an implicit expectation that you're going to use that update server instead of another one.
Possibly, but when the owner of that server comes around and starts playing hardball, you probably need to figure out real quick how to mollify them or get out from under them. And if you're going to just point to the software license and say "it doesn't say I have to do anything to give back to you", then you probably shouldn't be surprised when the owner of the software points right back at the license and says "it doesn't say I have to give you access to the hard coded URLS either"
Except, as far as I understand this (not being a WPE customer or a WP user, just an observer), MM isn't cutting off WPE, he's cutting off anyone that uses WPE to host WP sites. The whole situation stinks and innocent customers are being caught in the crossfire as a result. No one comes out of this looking good and the WP community as a whole takes a hit as a result.