#atom

Copyleft license that ensures software remains free and open

Core Idea: The GNU General Public License (GPL) is a free software license that guarantees end users the freedom to run, study, share, and modify the software while requiring that any derivative works remain under the same license terms.

Key Elements

License Versions

• GPLv1 (1989): Original version
• GPLv2 (1991): Added "Liberty or Death" clause
• GPLv3 (2007): Added anti-tivoization and patent provisions
• LGPL: Lesser GPL for libraries with linking exceptions
• AGPL: Affero GPL addressing network service loophole

Core Requirements

• Distribution of source code alongside binaries
• Inclusion of license text with distributions
• Preservation of copyright notices
• Application of identical license to derivative works
• No additional restrictions on recipients' freedoms
• Prominent notices of modifications
• No discrimination against persons or fields of use

Copyleft Mechanism

• Viral nature requiring derivatives to maintain freedoms
• Distinction from permissive licenses (MIT, BSD)
• "Inheritance" of license terms to derivative works
• Definition of what constitutes a "derivative work"
• Compatibility considerations with other licenses
• Enforcement through copyright law
• Distinction between linking and aggregation

Legal Implications

• Copyright remains with original authors
• Infringement remedies available through courts
• Distributed enforcement through copyright holders
• Irrevocable license (once granted)
• Warranty disclaimers and liability limitations
• Jurisdictional considerations and global applicability
• Terminology precision affecting enforceability

Practical Application

1. Apply copyright notice to source files
2. Include full license text with software
3. Document any modifications to original code
4. Provide or offer complete source code
5. Preserve all existing notices and attributions
6. Add prominent modification notices
7. Ensure license compatibility for incorporated works

Connections

• Related Concepts: Free Software Movement (philosophical foundation), Copyleft (legal mechanism), Open Source Software (broader category)
• Broader Context: Software Licensing (legal framework), Intellectual Property in Software (parent field)
• Applications: Linux Kernel (prominent implementation), GNU Project Software (canonical usage)
• Components: License Compatibility (practical consideration), Software Distribution (implementation context)

References

1. Not specifically detailed in the provided source material

#GPL #Licensing #FreeSoftware #Copyleft #OpenSource #GNU

Connections:

Sources:

• From: Free Software Movement