Much as I applaud the effort and ideal to make something open, I guess you acknowledge that it's crazy to think Apple will ever cooperate.

iMessage, plus pressure on your friends to not break the text thread with green non-Apple bubbles, Facetime, tie-ins to the Apple hardware, Find my Friends, etc. are among the most important loyalty factors and moats against people leaving the Apple ecosystem.

Especially with people getting (as you admit) less satisfied with the hardware, they would be fools to open this up and let people leave.