GNU , a recursive acronym for GNU's Not Unix, project founded by Richard Stallman to promote free software.
The term GNU's Not Unix is a legal ploy to include the word Unix in the name, thus implying some relationship, while explicitly disclaiming a relationship by the same, potentially avoiding claims of trademark infringement. Moreover, RMS and other of GNU's principal authors resent Unix due to their experience with Lisp and other systems which they believe to be technically superior, yet (as history has shown) significantly less marketable and apparently less practical for reasons that make no sense to hackers. Worse is better [L1 ]. Thus, GNU was born as a trampoline from which an operating system superior to Unix might one day be developed, yet naturally Unix must first be implemented in order for GNU to be adopted.
GNU refers to various closely related things, but they all stem from Richard Stallman and the FSF's attempt to create a complete UNIX system that is completely free from commercial ties.
Tcl programmers should take note of two particular aspects of the GNU project:
gcc is called nowadays the GNU Compiler Collection, given the variety of front- and backends to the same internal engine.