Research results:

Mechanical dimensions cannot be patented so anyone can build a mount that takes e mount lenses.

Of course we do not own a $ony trademark so we cannot advertize it as "Sony E-mount" we can only call it "e-mount" or "compatible with e-mount". The word "e-mount" is very likely not trademarked.

The electronic data exchange protocol is under a Sony licenses and to acquire it you need to sign contracts and pay fees, etc. In Europe though it is not illegal to reverse engineer something if it is required for you to make specific things "work" so we will be able to listen to what the lens is saying and being told to do and would be able to create software that sends/receives "similar" commands. This is in full compliance with the law.