[ytjohn]

For tmux, that opens up pretty much any terminal based editor (vim, emacs, nano) along with all the extensions you might install with it (and the build environment).

But for a protocol, I think what EtherPad (and google wave) had done with cell by cell action is what's needed. If google wave had taken off (and actually implemented their federation concept), I could definitely see people creating plugins to send and receive character operations via a google wave server.