To the best of my knowledge - i.e., I've read somewhere - Emacs is a derivative in style from Lisp Machines at the MIT Lab. It's not really a Unix program.
Emacs predates the Lisp machines, btw. The original was written (as TECO macros) on ITS. The Lisp machines came out of the same culture and thus had their own emacsen. But GNU Emacs that we are all using today was written on Unix from day one.
There's a public access ITS system over in Sweden, or you can grab an emulator and run it yourself. I recommend trying it just so you can see how Emacs and Info have remained essentially the same (RMS's sad devotion to that ancient religion, etc)