Emacs: The Extensible, Customizable Display Editor (1981)

> Many people can contribute to the development of the system, for the most part without interfering with each other. This has led the EMACS system to become more powerful than any previous editor.

> User customization helps in another, subtler way, by making the whole user community into a breeding and testing ground for new ideas.

RMS wrote these words in 1981. Org mode was released in 2003 (! twenty years ago?!) and added functionality that for many users is much of what Emacs offers. Today there is a mature ecosystem of incredibly high quality packages, and Emacs itself continues to become even more extensible, with the underlying infrastructure helping “libraries” become even more well behaved and composable.

This part of the story alone is a staggering triumph, comparable to the success of the Linux kernel and all that it has become, absorbed, encompassed, and grown to nurture.