[koffiezet]

> beyond allowing others to send/receive messages

Just publishing the specs will not allow anyone to send/receive iMessages. It's built on a closed loop CA / certificate system.

Remember that Steve Jobs actually announced on-stage it would be an open protocol without actually discussing that with his engineers? The architecture is designed to be closed from the get-go, and opening up the iMessage ecosystem in it's current design is simply not possible without giving 3rd parties considerable access to Apple internals, affecting a ton of stuff beyond iMessage, and pose serious security risks.

Could Apple re-design a messaging system which would allow this and roll it out transparently to all it's users? Absolutely, but that would require a ton of engineering work, and won't be there tomorrow.