GNU stands for "[GNU]'s Not Unix" and is therefore a recursively-defined acronym. It 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. See http://www.gnu.org/ for details of what the project believes itself to be. Tcl'ers are recommended to take notice of two particular aspects of the GNU project: * '''[gcc]''', the GNU C Compiler, is by far and wide the most widely portable C compiler in the world, and it is (or should be) the aim of anyone developing the Tcl core (or common extensions) to compile completely cleanly using this compiler, even when all warnings are turned on. * the '''[GPL]''', GNU Public License, is a software license that is common among FSF developers and many others; however it is not at all favoured for the Tcl core as it is (in effect) severely restrictive of what commercial development may be done with it. IMHO it works better for applications, and though there is the [LGPL] (Lesser or Library GPL) and other derivative FSF sponsered licenses to address these sorts of concerns, Tcl's modified Berkeley license is still the currently preferred (and required for Tcl core work) license. '''gcc''' is called nowadays the GNU Compiler Collection, given the variety of front- and backends to the same internal engine. ---- [Category Acronym]