Free software movement

The free software movement advocates users’ freedom to run, study, modify, and share software. It treats these freedoms as ethical and social rights, not merely as practical advantages.

Free software: Software distributed with freedoms to run, study, modify, and share it. The movement’s central idea is defined by these four user freedoms.
Richard Stallman: An American programmer who founded the GNU Project and the Free Software Foundation. Stallman articulated the movement’s principles and organized its early institutions.
GNU General Public License: A copyleft software license that grants broad permissions and requires covered distributions to preserve those freedoms. The GPL is the movement’s best-known legal instrument for protecting user freedoms.
Proprietary software: Software whose license restricts users’ ability to inspect, modify, or redistribute it. The movement opposes these restrictions as a denial of users’ freedom.
Linux: A broad family of operating systems built around the Linux kernel and commonly distributed with free software. Linux-based systems demonstrate the scale a free software ecosystem can reach.
Four essential freedoms: The freedoms to run a program, study and change it, redistribute copies, and distribute modified versions. These four rights provide the movement’s standard test for software freedom.
GNU Project: A project launched in 1983 to develop a Unix-like operating system composed entirely of free software. GNU turned the movement’s political aims into a practical software-building effort.
GNU Lesser General Public License: A copyleft license designed to permit linking covered libraries with software under other licenses. The LGPL applies copyleft more narrowly than the GPL to encourage library use.
Open-source movement: An advocacy movement that emphasizes the practical benefits of openly available source code and collaborative development. It overlaps with free software but generally argues from different values and aims.
Debian: A community-developed operating system built primarily from free software and maintained by the Debian Project. Debian formalized commitments to software freedom in its community guidelines.

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