Other meanings of GNU
FREE SOFTWARE COLLECTION
GNU is a large collection of free software and the operating-system project that began in 1983 with the aim of giving users control over the programs they run, study, modify, and share.1 Its tools, libraries, documentation, and licensing principles helped establish the modern free-software movement and remain widely used in systems that also contain the Linux kernel.
GNU began as an operating-system project, but its lasting form is a broad ecosystem of compatible free-software packages. Richard Stallman announced the project in September 1983, seeking to create a complete Unix-like system whose users could share and change the code rather than depend on proprietary restrictions.1 The name “GNU” is a recursive acronym for “GNU's Not Unix”: it signals technical compatibility with Unix while distinguishing GNU from the Unix trademark and proprietary implementations.
The project grew from a practical response to increasingly restricted software environments at universities and research laboratories. Its early objectives included developing a kernel, compilers, editors, shells, libraries, and system utilities. GNU's work was not limited to writing code; it also treated user freedoms and the legal conditions for collaboration as central parts of software design.
GNU supplies many of the foundational components associated with Unix-like computing. The collection includes the GNU Compiler Collection, the GNU C Library, the Bash shell, the GNU Core Utilities, the GNU Debugger, GNU Emacs, the GNU Make build tool, and numerous networking, text-processing, development, and documentation programs.2
These packages are modular rather than a single monolithic product. A distribution can combine selected GNU programs with software from other projects, different kernels, graphical environments, and package-management systems. GNU tools therefore appear in servers, desktops, embedded devices, scientific systems, and development environments even when users do not identify the surrounding operating system as “GNU.” Their command-line interfaces and portable implementations also made them important across many hardware architectures.
GNU defines free software by the freedoms it grants users, not by whether it has a price. The four central freedoms are the freedom to run a program for any purpose, study and modify its source code, redistribute copies, and distribute modified versions.3 Access to source code is necessary for the freedoms to study and change the program.
The GNU General Public License expresses these principles through copyleft: permitted redistribution of a covered work must preserve the relevant freedoms and, under the license's conditions, make corresponding source available.4 Copyleft differs from simply placing software in the public domain or using a permissive license. It is intended to prevent improvements from being redistributed as closed software while still allowing commercial use, modification, and sale. The GPL has several versions; GPLv3 also addresses issues such as patent terms and hardware that technically prevents users from installing modified software.
Most systems commonly called “Linux” combine the Linux kernel with GNU programs and many other projects. The Linux kernel was released by Linus Torvalds in 1991, while the GNU project had already produced much of the surrounding user-space software needed for a functioning Unix-like environment.1 This combination is often described by the GNU Project and the Free Software Foundation as “GNU/Linux.”
The distinction concerns both history and emphasis. “Linux” precisely names the kernel, whereas a complete operating system includes system libraries, utilities, shells, installers, applications, and other components. Not every Linux-based system uses GNU user-space software: Android, for example, uses the Linux kernel with a different user space. Conversely, GNU software also runs with kernels other than Linux, including the BSD kernels and experimental GNU Hurd kernel.
GNU's lesser-known work extends well beyond the utilities most visible in a terminal. The project maintains documentation systems such as Texinfo, language tools such as Bison and Flex, internationalization infrastructure, mathematical and scientific packages, and accessibility-related software. GNU also developed Guile, a programming-language framework intended to make applications extensible through Scheme.
The GNU Hurd is the project's own kernel design, built from a collection of cooperating servers running on top of a microkernel rather than from one large traditional kernel.5 It has been historically significant as an attempt to apply GNU's modular design to the operating-system kernel, although GNU/Linux became the dominant way GNU user-space tools were deployed.
GNU's influence also reaches education and public policy. Its licenses and definition of software freedom helped shape later free and open-source software communities, while its manuals and development tools became infrastructure for projects whose authors do not otherwise identify with the GNU movement.
“GNU” here refers to the GNU free-software collection and operating-system project, not other uses of the acronym.
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