It wasn't.
What he probably meant, that GNU Emacs (1984-...) was based on the code of another Emacs implementation, Gosling Emacs, which also had a commercial version.
The original EMACS was developed at MIT, 1976, by Guy L. Steele Jr. and David Moon.
Yea sorry for the misinformation. I'd read an earlier version of the Emacs wikipedia page that made it seem like Gosling Emacs was the original. The page is clearer now.