A Beginner’s Guide to Open Source Licenses
Introduction
Open-source software is an integral part of the tech world, driving innovation, collaboration, and accessibility. One key aspect of open-source projects is their licensing, which defines how the software can be used, modified, and shared. These licenses set the rules for both creators and users, ensuring that the open source ecosystem thrives on collaboration while respecting individual rights. In this article, we’ll delve into the ten most common open source licenses, exploring their nuances and providing examples of popular projects that use them.
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- GNU General Public License (GPL):
- The GPL is one of the most well-known copyleft licenses. It requires that derivative works also be open source and share-alike.
- GPL has different versions (GPLv2, GPLv3) with varying terms and conditions.
- Examples of GPL-licensed projects include the Linux kernel, the GNU tools, Ansible, etc.
- MIT License:
- MIT is a permissive license that allows almost unrestricted use, modification, and distribution.
- It’s simple and short, making it a popular choice for many projects.
- Examples of MIT-licensed projects include jQuery, ReactJS, Node.js, .NET, Rails, etc.
- Apache License 2.0:
- Apache 2.0 is another permissive license with an added patent grant clause, providing some protection against patent-related claims.
- It’s used by many Apache Software Foundation projects and Android.
- BSD License (3-Clause and 2-Clause):
- BSD licenses are permissive like MIT but come in 3-Clause and 2-Clause versions.
- They’re known for their brevity and allow for use in proprietary software.
- FreeBSD and LLVM use BSD licenses.
- Mozilla Public License (MPL):
- The MPL is a copyleft license that balances openness with compatibility with proprietary software.
- It allows mixing MPL code with proprietary code as long as the MPL code remains open source.
- Mozilla Firefox is an example of an MPL-licensed project.
- GNU Lesser General Public License (LGPL):
- LGPL is a variation of the GPL with more permissive terms for libraries.
- It allows dynamic linking to proprietary applications.
- GTK+ and GStreamer use LGPL.
- Eclipse Public License (EPL):
- EPL is designed for use with the Eclipse IDE but is suitable for other projects.
- It’s a copyleft license that requires derivative works to be open source when distributed.
- Eclipse IDE and BIRT use EPL.
- Common Development and Distribution License (CDDL):
- CDDL is designed for projects with collaborative development and mixed open and closed source components.
- It enforces openness for some components while allowing proprietary use for others.
- OpenSolaris is an example of a CDDL-licensed project.
- Artistic License:
- The Artistic License is used primarily for Perl projects.
- It allows for modification and distribution but often requires changes to be documented.
- Perl itself uses the Artistic License.
- Creative Commons Licenses (Various):
- Creative Commons licenses cover a wide range of content, including text, images, and media.
- They provide different levels of permissions, from fully open to more restrictive, allowing creators to choose how their work is shared.
Nuances and Considerations
When choosing an open source license for your project, consider the following nuances:
- Permissiveness vs. Copyleft: Decide how open you want your code to be. Permissive licenses allow more freedom, while copyleft licenses prioritise preserving open source status.
- Compatibility: Some licenses are compatible with each other, while others are not. Check whether your chosen license can be used with other licenses.
- Attribution: Determine if you require attribution in your project. Attribution means giving credit to the original creator or copyright holder of a work. It typically involves including the original copyright notice or author’s name in the derivative work or any distribution of the work.
- Patent Clauses: Some licenses, like the Apache License, include patent grant clauses to protect users from patent-related claims.
- Viral Effect: Copyleft licenses like the GPL have a “viral” effect, meaning derivative works must adopt the same license.
Check out https://choosealicense.com/licenses/ for more.
A comparison of the Apache License 2.0, MIT License, and GNU General Public License (GPL)
| Aspect | Apache License 2.0 | MIT License | GNU General Public License (GPL) |
|---|---|---|---|
| License Type | Permissive Open Source License | Permissive Open Source License | Copyleft Open Source License |
| Usage and Modification Rights | Allows modification, use, and distribution | Allows modification, use, and distribution | Allows modification, use, and distribution |
| Commercial Use | Permits use in both commercial and non-commercial projects | Permits use in both commercial and non-commercial projects | Permits use in both commercial and non-commercial projects |
| Attribution | Requires attribution in the form of notices and disclaimers | Requires attribution in the form of the original copyright notice | Requires attribution and preservation of license text |
| Patent Grant | Includes a patent grant clause to protect contributors and users from patent-related claims | Lacks explicit patent grant provisions | No specific patent grant, but GPLv3 has some patent clauses |
| Copyleft Effect | No copyleft effect (doesn’t require derivative works to be open source) | No copyleft effect (doesn’t require derivative works to be open source) | Strong copyleft (requires derivative works to be open source) |
| Compatibility | Compatible with other open-source licenses, including the GNU GPL | Compatible with other open-source licenses, including the GNU GPL | Typically not compatible with permissive licenses |
| Derivative Works | Allows modification without requiring derivative works to be open source | Allows modification without requiring derivative works to be open source | Requires derivative works to be open source |
| Proprietary Integration | Permits integration with proprietary software | Permits integration with proprietary software | Typically prohibits integration with proprietary software |
| License Notice Requirement | Requires inclusion of license notices and disclaimers | Requires inclusion of the original copyright notice | Requires inclusion of the GPL license text and notices |
| Contributor License Agreement (CLA) | Some Apache projects may require contributors to sign a CLA, granting certain rights to the project | Typically, MIT-licensed projects do not require contributors to sign a CLA | Some projects may require contributors to assign copyright |
| Liability and Warranty | Offers no warranties or guarantees and includes a liability disclaimer | Offers no warranties or guarantees and includes a liability disclaimer | Offers no warranties and includes a liability disclaimer |
| Viral Nature (Effect on Derivative Works) | Non-viral (derivative works are not required to be open source) | Non-viral (derivative works are not required to be open source) | Viral (derivative works must adopt the GPL) |
Conclusion:
Understanding open-source licenses is crucial for developers, contributors, and users of open-source software. Each license has its own set of terms and conditions that can significantly impact how a project is used and shared. Whether you prioritise permissiveness or require copyleft provisions, there’s a license that suits your project’s goals and values. Make sure to carefully select the license that aligns with your project’s vision, and consider seeking legal counsel when necessary to ensure compliance with open-source licensing requirements.