SXEmacs is a fork of the XEmacs text editor. It runs on many Unix-like operating systems, and 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. Any user can download SXEmacs as free software available under Version 3 of the GNU General Public License.
The software community generally refers to FSF GNU Emacs, XEmacs, SXEmacs (and a number of other similar editors) 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: