SXEmacs
SXEmacs is a fork of the XEmacs text editor.
It runs on many Unix-like operating systems including OS X. It is notable for features such as FFI support, enhanced number types, raw string regexps, and an implementation of Pugh's skip lists.History
On December 31, 2004, Steve Youngs announced the creation of SXEmacs on the emacs-devel and xemacs-beta mailing lists.
The software community generally refers to GNU Emacs, XEmacs, SXEmacs collectively or individually as emacsen or as Emacs, since they all take their inspiration from the original TECO Emacs.
The reasons he cited for the fork were:
