That and some other things. There were also several forks of GNU Emacs and Xemacs to support Mac OS Carbon/Cocoa, of which Aquamacs is still in widespread use.
There's also Steve Youngs' SXEmacs (a XEmacs fork), which is probably the most well-developed of several efforts to extend Emacs to be a window manager.
There's also Steve Youngs' SXEmacs (a XEmacs fork), which is probably the most well-developed of several efforts to extend Emacs to be a window manager.