I think johnw tried at some point but Yamamoto isn't very excited at the prospect, and who would really blame him?
Keeping his work out of the main branch gives him the freedom he needs to focus on technical matters and introduce support for new features as they're being exposed by OSX APIs.
As long as Stallman holds sway over Emacs and can demand that one cripple his own work for _political reasons_ , I don't see this situation changing. I'm just glad that Yamamoto did not fall for the "lowest common denominator" approach and has enough pride in his own work to do things as he sees fit.
GNU Emacs is a political project, rooted in the free software movement. Too often people like you insult Stallman and ask for an Emacs that is a bit better technically in exchange for removing the goals of the GNU proejct. There's plenty of other software to use that cares about technical matters only.
Even so, it would help if Homebrew reassigned the "emacs" package name to the Emacs fork by Yamamoto Mitsuharu.
(The way it is now, when you install with `brew install emacs`, you get FSF emacs; to get Mitsuharu Emacs, you have to know to say `brew install emacs-mac` instead.)
I saw later in the thread that you're Daniel. I enjoy your emacs-devel posts and your back&forths with Eli/Stefan. I liked (and was in full agreement with) your commentary during Emacs dynamic modules dev, and I also enjoyed your recent demand paging post.
It's just too bad that you seldom get things to go your way.