The GNU Manifesto was written by Richard Stallman and published in March 1985 in Dr. Dobb's Journal of Software Tools as an explanation and definition of the goals of the GNU Project, and to call for participation and support. It is held in high regard within the free software movement as a fundamental philosophical source. The full text is included with GNU software such as Emacs, and is available on the web.
The GNU Manifesto begins by outlining the goal of the project GNU, which stands for GNU's Not Unix. The current contents of GNU at the time of writing are then described and detailed. Richard Stallman then goes into an explanation of why it is important that they complete this project. The reason he explains is based on Unix becoming a proprietary software. It then explains how people can contribute to the project, and also why computer users will benefit from the project. A large part of the GNU Manifesto is also focused on rebutting possible objections to GNU's goals. Objections described here include the programmer's need to make a living, the issue of advertising/distributing free software, and the perceived need for monetary incentive. Most of this text explains how the free software philosophy works, and why it would be a good choice for the technology industry to follow.