Licensing is at the heart of how software developers, artists, educators, and other creators share their work with the world. Two prominent families of licenses—open source and Creative Commons—enable creators to share, adapt, and build upon each other’s work, all under specific obligations and conditions. This blog post offers a detailed, graduate-level look at key open source licenses and the full spectrum of Creative Commons licenses, highlighting the freedoms and obligations they confer on users and developers.
Disclaimer: This post is intended for general informational purposes and does not constitute legal advice. Always consult a qualified attorney if you have specific questions about how these licenses apply to your situation.
AI Use Disclosure: In addition to my regular AI Use Disclosure, I note that I used AI for some of the research and content in preparing this piece. It’s still me, but my commitment to transparency means I want you to know that in writing this article, I had help.
1. Introduction to Licensing Philosophy
Before diving into the specifics, let’s briefly outline the philosophical underpinnings that distinguish open source from more restrictive licenses:
- Open Source Licenses:
- Typically focus on software.
- Encourage collaboration and sharing of source code.
- Vary in their level of “copyleft,” i.e., the obligation to re-share modifications under the same or similar license terms.
- Can contain poison pills, like licenses to other IP and requirements to publish custom code written to work with the licensed software. Well, they’re not really poison pills, but they could pose a problem in due diligence for investors or acquirers.
- Creative Commons Licenses:
- Typically focus on creative content (text, images, music, videos, etc.).
- Provide straightforward, modular permissions and conditions (e.g., attribution, non-commercial use, share-alike requirements).
- Aim to create a global “commons” of creative works that others can build upon.
Understanding the specifics of each license is essential for ensuring compliance and maximizing the benefits of collaborative, open distribution.
2. Major Open Source Licenses
This is a convenient summary of the licenses, but this is absolutely not a substitute for advice from a licensed attorney familiar with copyright law. The penalties for infringing copyright can be quite significant, so you must not rely on these descriptions for legal purposes. In other words, read the original document and have your lawyer explain it to you. A summary will inevitably miss some important stuff. This isn’t legal advice!
2.1 GNU General Public License (GPL)
- Overview: The GNU General Public License (GPL) is one of the earliest and most influential copyleft licenses, originally authored by Richard Stallman for the Free Software Foundation.
- Key Versions:
- Obligations:
- Source Code Distribution: When you distribute software (in source or binary form) derived from GPL-licensed code, you must provide access to the complete source code.
- Copyleft Requirement: Any modifications, derivative works, or combined software must also be distributed under the same GPL license.
- No Additional Restrictions: You cannot impose further limitations on the recipients’ exercise of the rights granted by the GPL.
- Typical Use Cases: Projects that strongly value ensuring future modifications remain open-sourced (e.g., the Linux kernel uses GPLv2).
2.2 GNU Lesser General Public License (LGPL)
- Overview: Formerly known as the “Library GPL,” the LGPL is a weaker copyleft license intended primarily for software libraries.
- Key Differences from GPL:
- Linking Exception: You can link proprietary software to an LGPL library without the proprietary code falling under the GPL’s copyleft.
- Copyleft Limited to the Library: Modifications to the LGPL code itself must remain open, but your own code that merely interfaces with the library does not.
- Obligations:
- If you modify the library’s source code, you must distribute those modifications under the LGPL.
- You must allow users to re-link or modify the library in their copy of the software.
- Typical Use Cases: Libraries that want to encourage broad commercial and open source adoption without forcing the entire application to be open source.
2.3 MIT License
- Overview: The MIT License is one of the most permissive and popular open source licenses.
- Obligations:
- Preserving Copyright Notice: If you distribute MIT-licensed software, you must include the license text and copyright notice.
- No Copyleft Requirement: You are free to redistribute and even re-license the code under different terms, including proprietary licenses.
- Typical Use Cases: Web frameworks (like Ruby on Rails), JavaScript libraries, and many projects that prioritize minimal legal friction and maximum freedom.
2.4 BSD Licenses (2-Clause and 3-Clause)
- Overview: The Berkeley Software Distribution (BSD) licenses are closely related to the MIT License in their permissive approach.
- Key Variants:
- 2-Clause BSD (aka “Simplified BSD”): A short, highly permissive license.
- 3-Clause BSD (aka “New BSD”): Similar but adds a clause preventing endorsement of derivative products by the original authors.
- Obligations:
- Include Copyright Notice: Similar to MIT, you must keep the license text intact.
- No Copyleft: Allows incorporation into proprietary software.
- Typical Use Cases: Operating systems (e.g., FreeBSD), networking tools, and widely-used libraries that aim to be easily integrable into any type of project.
2.5 Apache License 2.0
- Overview: Created by the Apache Software Foundation, the Apache License 2.0 is permissive but includes provisions on patent usage.
- Obligations:
- License and Notice: Must retain copyright and license notices.
- Patent Grant: Contributors grant a royalty-free, worldwide patent license for any patents they hold that are essential to the project.
- No Strong Copyleft: Like MIT/BSD, Apache does not require modifications to be open-sourced, though it does have certain file-level attribution requirements.
- Typical Use Cases: Apache web server projects, large-scale open source ecosystems (such as Hadoop), and other infrastructure software where patent protection is a concern.
2.6 Mozilla Public License (MPL) 2.0
- Overview: The MPL 2.0 is a file-based copyleft license, which means modifications to MPL-licensed files must be shared, but you can combine MPL-licensed files with other files under different licenses.
- Obligations:
- Source Code Disclosure: If you modify MPL-licensed source code files, you must distribute those changes under the MPL.
- File-Level Copyleft: Only the modified MPL files are subject to copyleft; larger works that use MPL code can be licensed differently as long as the MPL files remain under MPL.
- Typical Use Cases: Firefox, Thunderbird, and other Mozilla projects. Ideal for those who want copyleft for certain files but still allow broader proprietary integrations.
2.7 Eclipse Public License (EPL)
- Overview: The EPL is used for many Eclipse Foundation projects. It places certain distribution requirements on the program’s source code but not as extensively as the GPL.
- Obligations:
- Copyleft-Like Provisions: Modifications to EPL-licensed code must be shared if you distribute them.
- Patent Clause: Similar to Apache, there is a patent grant but also a patent retaliation clause if you sue other contributors for patent infringement.
- Typical Use Cases: Java-based tools, Eclipse IDE, and related plug-ins.
3. Major Creative Commons Licenses
This is a convenient summary of the licenses, but this is absolutely not a substitute for advice from a licensed attorney familiar with copyright law. The penalties for infringing copyright can be quite significant, so you must not rely on these descriptions for legal purposes. In other words, read the original document and have your lawyer explain it to you. A summary will inevitably miss some important stuff. This isn’t legal advice!
Creative Commons (CC) licenses are modular. Each license specifies certain permissions and restrictions, indicated by letter abbreviations. The core components include:
- BY (Attribution): Requires users to credit the original creator.
- NC (Non-Commercial): Prohibits use for commercial purposes.
- SA (ShareAlike): Requires derivative works to be licensed under the same or compatible terms.
- ND (No Derivatives): Prohibits modification of the work.
Below are the most common CC licenses, each fulfilling a different balance of openness and restrictions.
3.1 CC BY (Attribution)
- Overview: The most open of the standard CC licenses (except for CC0, see below), CC BY requires only that you credit the creator.
- Obligations:
- Must provide attribution in the manner specified by the licensor.
- Rights Granted:
- You can copy, redistribute, transform, and build upon the work for any purpose (commercial or non-commercial), as long as you give proper credit.
- Typical Use Cases: Academic papers, artwork, photographs, educational materials when creators want maximum distribution while retaining a credit requirement.
3.2 CC BY-SA (Attribution–ShareAlike)
- Overview: Similar to CC BY, but SA imposes a share-alike (copyleft-like) condition for derivative works.
- Obligations:
- Attribution: As with CC BY, you must credit the original creator.
- ShareAlike: Any derivative work must be licensed under the same or a compatible license (i.e., it must allow similar freedoms).
- Rights Granted:
- Commercial and non-commercial use, alteration, etc., are all allowed, provided derivative works remain under CC BY-SA (or a compatible license).
- Typical Use Cases: Wikipedia articles, open educational resources that aim to preserve openness in all future adaptations.
3.3 CC BY-NC (Attribution–NonCommercial)
- Overview: Allows re-use and modification of the work, but only for non-commercial purposes.
- Obligations:
- Attribution: Must credit the creator.
- Non-Commercial Only: You cannot profit from the use of the work or any derivative directly.
- Rights Granted:
- Copying, redistributing, and creating derivative works for non-commercial purposes.
- Typical Use Cases: Personal blog posts, artworks, or other content where the creator wants to prevent direct commercial exploitation without permission or separate licensing.
3.4 CC BY-NC-SA (Attribution–NonCommercial–ShareAlike)
- Overview: This license adds both non-commercial and share-alike restrictions to the baseline CC BY.
- Obligations:
- Attribution: Must credit the creator.
- Non-Commercial: Derivative works cannot be used commercially.
- ShareAlike: Must license derivatives under the same license.
- Rights Granted:
- You may remix, adapt, and build upon the work non-commercially.
- You must share any adapted works under the same terms.
- Typical Use Cases: Open educational materials, non-profit campaign content, or collaborative projects that bar commercial usage but require continuing openness.
3.5 CC BY-ND (Attribution–NoDerivatives)
- Overview: Permits redistribution of the work (including commercial distribution), but no changes can be made.
- Obligations:
- Attribution: Must credit the creator.
- No Derivatives: You cannot modify the original material or create derivative works based on it.
- Rights Granted:
- You can freely share (copy and redistribute) the unmodified work, even for commercial purposes, but cannot alter it.
- Typical Use Cases: Photographers or artists who want widespread sharing (potentially including commercial contexts) but want to preserve the integrity of the original work.
3.6 CC BY-NC-ND (Attribution–NonCommercial–NoDerivatives)
- Overview: The most restrictive standard CC license.
- Obligations:
- Attribution: Must credit the creator.
- NonCommercial: No commercial use allowed.
- NoDerivatives: You cannot modify the original material.
- Rights Granted:
- You can share the work for non-commercial purposes only, and you cannot alter it.
- Typical Use Cases: Personal essays, photographs, or recordings that an author wants to circulate, but with minimal permissions to ensure no alterations or commercial uses occur without explicit authorization.
3.7 CC0 (Public Domain Dedication)
- Overview: Not technically a license but a public domain dedication. The creator waives all possible rights to the extent allowed by law.
- Obligations:
- None: The user has no legal obligation to attribute or share derivatives under similar terms, although best practice encourages crediting the original author.
- Rights Granted:
- Essentially all rights. The work can be used, shared, and remixed for any purpose—commercial or non-commercial—without any requirement to credit or share.
- Typical Use Cases: Data sets, certain scientific works, and “open data” initiatives intended to maximize reusability without restriction.
4. Constitutional Copyright License
US Copyright law originally limited copyright to a 14 year term, extended for another 14 if the author was still alive when the original term expired. Modern copyright law provides for such long copyright terms that a work created on the day a baby is born is almost certain to remain copyright protected until well after that baby has lived a full life and died of old age.
I created a license that places a work under the terms that the US Founders thought the copyright clause would result in. That Constitutional Copyright License is found here. After creating the document, I learned that I was not the first person to try to create a license using that idea — so I should not get credit for the idea.
5. Balancing Obligations and Freedoms
When choosing a license, creators should weigh several factors:
- Community and Ethical Goals:
- Do you want to ensure modifications remain open (copyleft/share-alike)?
- Or do you want to encourage maximum adoption (permissive license)?
- Commercial Considerations:
- Is commercial use acceptable, or do you want to limit derivatives to non-commercial contexts?
- Integration Requirements:
- Will your work be combined with other open source projects with specific licensing rules?
- Some licenses are incompatible with others, particularly strong copyleft licenses like the GPL.
- Legal Risks:
- Patent grants and patent retaliation clauses (in Apache, EPL, etc.) may play into your long-term strategy.
- CC licenses do not cover patents but focus on copyright. If your work involves technology, consider how patents intersect with your chosen license.
- Re-read this section. It’s that important.
6. Conclusion
Open source and Creative Commons licenses are powerful tools for shaping how creative and technical works are shared, distributed, and built upon. While open source licenses focus primarily on software code, Creative Commons licenses address creative content more broadly. Both ecosystems share core principles of freedom and collaboration, but each license comes with its own set of obligations—ranging from requiring attribution to mandating that derivative works remain open under the same license terms (copyleft or share-alike).
By understanding the details of these licenses, you can select the best tool for your goals, whether that’s maximal freedom to innovate, guaranteed openness for future generations, or a specific constraint around non-commercial or share-alike use. With a thoughtful approach to licensing, you can help foster a culture of collaboration and creativity—while protecting your rights and the rights of your community.
Disclaimer: This post is intended for general informational purposes and does not constitute legal advice. Always consult a qualified attorney if you have specific questions about how these licenses apply to your situation.