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

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.