GNU General Public License (GNU GPL)
The GNU General Public License, commonly known as the GPL, is a widely used free software license that guarantees end users the freedom to run, study, share, and modify the software. Here is an in-depth look into its history, features, and significance:
History and Origin
- The GNU Project, launched in 1983 by Richard Stallman, aimed to create a completely free operating system. The GPL was developed as a means to ensure the software produced by the project remained free and modifiable.
- The first version of the GPL, GPLv1, was released in 1989. It was designed to prevent proprietary software from incorporating free software without giving back to the community.
- GPLv2 was released in 1991, addressing several issues found in the first version, particularly around the ambiguity of derivative works and linking.
- In 2007, GPLv3 was introduced to address new issues like software patents, tivoization (hardware restrictions), and to strengthen the license against potential misuse.
Key Features
- Copyleft: This is the core principle of the GPL. It ensures that any derivative works or distributions of the software must also be distributed under the GPL, preventing proprietary forks.
- Source Code Availability: The GPL requires that the source code of the program must be made available whenever the software is distributed.
- Four Essential Freedoms:
- To run the program as you wish, for any purpose.
- To study how the program works, and change it to do what you wish.
- To redistribute copies to help others.
- To distribute copies of your modified versions to others.
- Compatibility with Other Licenses: While GPL is known for its strict copyleft, there are provisions for compatibility with other free software licenses through mechanisms like the GPL's "or any later version" clause and through the use of GPL-compatible licenses.
Impact and Significance
- The GPL has significantly influenced the software industry by promoting the development of free and open-source software. It's used by many major software projects including the Linux kernel.
- It has sparked debates and legal battles over software freedom, proprietary software, and intellectual property rights.
- The license has been instrumental in shaping public perception and legal understanding of software as a shared resource rather than a proprietary product.
Controversies and Criticisms
- Some critics argue that GPL's copyleft nature can be restrictive for developers who wish to incorporate GPL code into proprietary software.
- There have been issues regarding compatibility with other open-source licenses, leading to the creation of the LGPL (Lesser General Public License) for libraries.
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