Well, no. iMessage protocol was reverse engineered, but they patched it and make really hard to do crypto part of it. Hard enough that people stopped trying - a

Well, no. iMessage protocol was reverse engineered, but they patched it and make really hard to do crypto part of it. Hard enough that people stopped trying - after all you still required an existing registration from Apple's device and there was no guarantee it stops working again. What they do is run ichat2json every time there is a new message in a folder and AppleScript to send outgoing messages. It requires a macOS with already authenticated Messages.app. It's not using any unofficial APIs, it's just a wrapper around iMessage client on a mac.