GNU is a Unix-like computer operating system developed by the GNU Project, ultimately aiming to be a "complete Unix-compatible software system" composed wholly of free software. Development of GNU was initiated by Richard Stallman in 1983 and was the original focus of the Free Software Foundation (FSF). The latest alpha release of the GNU system is GNU 0.401, released on 1 April 2011, featuring GNU Hurd as the system's kernel. Other (non-GNU) kernels, most famously the Linux kernel, can also be used with GNU. The FSF maintains that Linux, when used with GNU tools and utilities, should be considered a variant of GNU, and promotes the term GNU/Linux for such systems, (leading to the GNU/Linux naming controversy). GNU is a recursive acronym for "GNU's Not Unix!", chosen because GNU's design is Unix-like, but differs from Unix by being free software and containing no Unix code. Programs released under the auspices of the GNU Project are called GNU packages or GNU programs.
Contributions by Gronky, CYD, and Rmstallman.