The original can be found http://www.coulouris.net/cs_history/em_story/
Inspired by em, and by their own tweaks to ed, Bill Joy and Chuck Haley, both graduate students at UC Berkeley, took code from em to make en, and then "extended" en to create ex version 0.1.
Note: The notion of "visual" is relative. I don't know if other versions where closer to the current notion of visual, but this one is relatively far from "a one line vi". A more visual mode was implemented on more capable terminals, unfortunately this doesn't appear in the available source code.
When you press o, the line is not displayed moving through the line displays it, the delete words operations cause the line to be redisplayed on a new line. Deleting a char backward cause a # to be displayed after the character....just try it!
Feel free to report bugs, or send comments to pierre.gaston@gmail.com
Some notes about the port: