Why do you think Apple is immune to patent lawsuits? They have frequently had to settle them.

It would obviously be useless if they released the spec for it but you couldn't use it to connect to existing FaceTime devices.

That's the problem. They cannot because one of the technologies they're using is covered by an existing patent that doesn't allow them to open it up. They would have to re-engineer how the whole system works to make it different enough to not be applicable to that patent.

To be clear, the patent in question is reaaaaaaally generic so there's really nothing they can do to get around it while still keeping a video-calling system that allows people to call with an Apple ID.

Apple is already on the hook for about a billion dollars to VirnetX. That's not a lame excuse at all.