The GNU Initial Announcement, posted by stallman to the USENET newsgroup net.unix-wizards on September 27, 1983, is the founding document of the gnu-project — predating the gnu-manifesto by approximately 18 months. In fewer than 500 words, it declared stallman's intention to write a complete free Unix-compatible operating system and invited programmers to join the effort.
The announcement is blunt and practical. stallman declares his intention — "Starting this Thanksgiving I am going to write a complete Unix-compatible software system called GNU" — and asks for donations of time, money, hardware, and equipment. He was still employed at mit-ai-lab when he posted it; he resigned from MIT employment in January 1984 to avoid conflicts of interest over distributing GNU as free software. The name GNU is introduced with the recursive joke that would become famous: "GNU's Not Unix." The technical scope is outlined: a kernel, compiler, editor, and all the other components needed for a complete system.
What makes the announcement historically significant beyond its news value is its explicit framing of the project in ethical terms from the very first sentence. stallman does not merely say he wants to write free software as a technical exercise; he says he wants to give software users the freedom to share and modify software. This is the earliest public articulation of what would become the four-freedoms framework and the basis for the free-software-definition.
The announcement-of-gnu-project is also a declaration of intent against the direction the software industry was taking in the early 1980s. The dissolution of the open sharing culture at mit-ai-lab during the period mit-ai-lab-hacker-culture-1971-1984, and the rise of proprietary software firms like Symbolics, gave stallman direct personal experience of what software restrictions meant. The announcement is his response: not complaint but construction.
steven-levy's hackers-levy and Sam Williams's free-as-in-freedom-williams both provide context for the circumstances that produced this announcement. stallman had been the last holdout of the old AI Lab hacker culture; when the community fragmented, he chose to rebuild rather than adapt. The announcement is the first public artifact of that decision, and everything else — the gnu-manifesto, the free-software-foundation, the gpl-v1, copyleft — follows from it.