XEmacs [SEP] based on
XEmacs
XEmacs is a graphical- and console-based text editor which runs on almost any Unix-like operating system as well as Microsoft Windows. XEmacs is a fork, based on a version of GNU Emacs from the late 1980s. Any user can download, use, and modify XEmacs as free software available under the GNU General Public License version 2 or any later version.
History.
Between 1987 and 1993 significant delays occurred in bringing out a new version of GNU Emacs (presumed to be version 19).
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 (similar to bignums in XEmacs 21.5), raw string regexps, and an implementation of Pugh's skip lists.
History.
On December 31, 2004, Steve Youngs (lead developer) announced the creation of SXEmacs on the emacs-devel and xemacs-beta mailing lists.
The software community generally refers to