@fabionatali might want to check https://github.com/larsbrinkhoff/emacs-history if you actually want to try, I bet anything before the early nineties will be harder to build on a modern unix.
The patch set for emacs 18 in https://dev.gentoo.org/~ulm/emacs/ probably has hints needed to port anything much older, 18.59 is from 1992, so already more than a decade after Stallman's report you linked, and somehow more than 30 years old now. It's also the oldest version in https://ftp.gnu.org/old-gnu/emacs/
@djuber @fabionatali Here's a presentation where I demo TECO, Emacs from 1976, and some other things. Another time I demoed E (from Stanford), Gosling Emacs, and GNU Emacs 16, but that video is not available yet.
https://www.youtube.com/watch?v=xdJtANtJMIg