Emacs

From Hackers-IL

"Emacs is an operating system that just happens to know how to edit files."

"Emacs is a nice operating system, but what it lacks to compete with Linux is a good text editor."

These are some of the jokes that people tell about Emacs. What started as a text editor, is now also capable of reading mail, browsing the web, chatting on the IRC (and don't forget "M-x doctor"...) and many other things many people fill don't belong in an editor.

The history of Emacs is outlined in this chapter from Richard M. Stallman biography.

It eventually forked into two competing products: GNU Emacs and XEmacs, but they both still share a lot of code. And both are open-source.