On September 27, 1983, stallman posted to the net.unix-wizards Usenet newsgroup announcing the gnu-project — a plan to write a complete Unix-compatible operating system that would be freely available to all users. The announcement-of-gnu-project was both technical and political: the system would be technically capable (a complete Unix clone) and philosophically principled (software that users could run, study, modify, and redistribute without restriction).
The gnu-manifesto, published in 1985 in Dr. Dobb's Journal, elaborated the argument. It is simultaneously a technical announcement, a philosophical statement, and a fundraising appeal. The manifesto introduced the concept of "free software" not as freeware (zero price) but as software that respects user freedom — the distinction Stallman later crystallized as libre-vs-gratis. The manifesto also introduced the concept of copyleft: the idea that the copyright in free software could be used to require that derivative works also be free.
The free-software-foundation was incorporated on October 4, 1985, as a 501(c)(3) nonprofit to provide institutional support for the GNU project. The FSF's formation gave the project legal standing, the ability to hold copyrights, and a structure for accepting donations and employing developers. The founding-of-fsf event formalized what had been an informal one-person project.
The period 1985–1991 saw the production of the core GNU tools. GNU Emacs — the first major GNU release, described in gnu-emacs-first-release — was released in 1985, and Stallman's gnu-emacs-manual became a model of free documentation. The GNU C Compiler (GCC), released in 1987, was more strategically significant: a compiler is the tool that builds all other software, and a free compiler meant that all software built with it could in principle be built and modified by its users. Other tools followed: bash, glibc, binutils.
The free-software-definition was formalized during this period, codifying the four-freedoms: the freedom to run the program (freedom 0), the freedom to study and modify it (freedom 1), the freedom to redistribute copies (freedom 2), and the freedom to distribute modified versions (freedom 3). The numbering beginning at zero was itself a deliberate signal to the programmer audience.
The gpl-v1 was released in February 1989, formalizing the copyleft mechanism in legal language. Where earlier software had been distributed with informal "don't take this private" conditions, the GPL used copyright law's own enforcement mechanism to guarantee freedom: any distributor of GPL software must provide source code and must license any modifications under the same terms. eben-moglen later described this as legal judo — using copyright against itself. The drafting of the GPL marked the transition from the free software movement's philosophical phase to its legal-institutional phase.
By 1991, the GNU project had most of the components needed for a complete free operating system — but not the kernel. The gpl-and-linux-era-1991-1998 era begins with the piece that would fill that gap.