GNU Emacs release dates

[Miles Bader]

Gosmacs certainly didn't borrow any code from the earlier (original)
emacs, it was an utterly and completely different beast (I spent a lot
of time perusing both gosmacs and ITS Emacs source code as an
undergraduate).  Even the user-interface was different in many ways --
it was mostly the general concepts and most common command bindings
that were based on ITS emacs.

The later GNU Emacs in turn borrowed[*] not just some code, but UI
concepts from gosmacs as well, e.g. the user of ordinary buffers for
displaying completion and the like instead of using "typeout" like ITS
Emacs did.

[*] I suppose it may simply be a case of both "doing the obvious thing" though.