In 2016 Lars Brinkhoff emailed:
I have started working on preserving Emacs software:
https://github.com/larsbrinkhoff/emacs-history
Would this be of any interest to the Software Preservation Group?
I immediately agreed: Emacs has a long and honorable history with many implementations, and Lars is a skilled and prolific retro-computerist. By August of this year as I worked to rejuvenate the Software Preservation web site, I noticed that the Emacs page listed the major implementations of Emacs, but did not actually link to the content, whereas Lars’s github repository is filled with source code for a wide variety of implementations and a README that gives detailed provenance. After consulting with Lars, I revised the Software Preservation project to create a presentation layer detailing all the information in his GitHub repository. You can trace the history from the original version written in TECO macros, the Lisp Machine versions, TVmacs in the Architecture Machine Group, Multics Emacs, Prime Emacs, Montgomery Emacs, Gosling Emacs, Zimmerman Emacs, GNU Emacs (and its derivatives), Epsilon, and MicroEMACS.
If you think others should be included, you’ll have to convince Lars.