* '''Richard Stallman''' published the GNU Manifesto in 1984, which described the need for Free Software (“Free in the sense of free speech, not free beer”).

** The resultant GNU project developed free, open source replacements for most of the Unix programs, but not for the Unix kernel (the core program that interacted with and controlled the hardware).

** These programs were released under the GNU General Public License (GPL), which permits anyone to copy, use, and modify the software, as long as these rights are preserved for anyone receiving a subsequent copy of the software.

* In 1991, '''Linus Torvalds''', a Finnish computer programmer, released the Linux kernel, eventually placing it under the GPL.

** The Linux kernel, GNU software, and some other components can be combined into a powerful, Unix-like operating system (it can’t technically be called Unix, because it has never been certified to be Unix, but virtually everyone in the industry regards it as such).

** The combined GNU and Linux system is called GNU/Linux by some but just Linux by others (much to the dismay of Richard Stallman, who feels that the simple name Linux downplays the tremendous contribution made by the GNU Project).