GNU Emacs
In 1984, Stallman began working on GNU Emacs to produce a free software alternative to Gosling Emacs; initially he based it on Gosling Emacs, but he replaced the Mocklisp interpreter at its heart with a true Lisp interpreter, which entailed replacing nearly all of the code. It became the first program released by the nascent GNU Project. GNU Emacs is written in C and provides Emacs Lisp (itself implemented in C) as an extension language. Version 13, the first public release, was made on March 20, 1985. The first widely distributed version of GNU Emacs was 15.34, which appeared later in 1985. Versions 2 to 12 never existed. Earlier versions of GNU Emacs had been numbered "1.x.x", but sometime after version 1.12 the decision was made to drop the "1", as it was thought the major number would never change.
GNU Emacs was later ported to Unix. Since it had more features than Gosling Emacs, in particular a full-featured Lisp as extension language, it soon replaced Gosling Emacs as the de facto Emacs editor on Unix. A security flaw in GNU Emacs' email subsystem was exploited by Markus Hess in his 1986 hacking spree to gain superuser access to Unix computers.
Until 1999, GNU Emacs development was relatively closed, to the point where it was used as an example of the "Cathedral" development style in The Cathedral and the Bazaar. The project has since adopted a public development mailing list and anonymous CVS access. Development took place in a single CVS trunk until 2008, and today uses the Bazaar DVCS.
Richard Stallman remained the maintainer of GNU Emacs through most of the time, but took several breaks. The latest one persists and started 2008, when maintenance was handed over to Stefan Monnier and Chong Yidong.