Wow. Nowadays the ability to use Emacs is considered one of the pinnacles of technical accomplishment.
DLW later wrote a different Emacs implementation in Lisp, Zwei, for the Lisp Machine, which was even more deeply intertwined in the system than Multics Emacs was in Multics. Zwei (Zwei was Eine Initially) followed Eine (Eine is not Emacs)
FWIW both programmers mentioned in that section, DLW (Dan Weinreb) and MRC (Mark Crispin), died relatively young.
Emacs has a rich history indeed with many other branches of the family tree than GNU Emacs.