The origin of XEmacs according to Richard Stallman (stallman.org)

For the sake of completeness, Richard P. Gabriel's account is here: http://www.dreamsongs.com/DiBona-OReillyLetter.html

And Jamie Zawinski's account of this is here: http://www.jwz.org/doc/lemacs.html

Forking. Sacrament, not a sin. But don't tell that to the prophets.