Demystifying Open Source Licenses

Open Source licenses are basically a legal way of telling people how your software or creative work can be used, modified, or distributed. Learn more about some popular licenses!

Demystifying Open Source Licenses
Photo by Sasun Bughdaryan / Unsplash

Open Source licenses are basically a legal way of telling people how your software or creative work can be used, modified, or distributed. But why do they exist? 🤔

They exist to promote and protect the principles of open-source development and help share your work with the community in an ethical way.


In the 1980s, Richard Stallman initiated the free software movement and founded the Free Software Foundation (FSF), which eventually led to the creation of GNU General Public Licenses (GPL). In 1998, a group of individuals, including Eric S. Raymond and Bruce Perens recognized the practical benefits of sharing source code and coined the term Open Source and formed The Open Source Initiative (OSI).

Why Open Source?

Open source lets one share their work with the public and work in public. Open source software creates a sense of transparency and privacy, and lets anyone add new features or fix bugs.

The OSI developed a set of criteria known as the Open Source Definition, which outlines the requirements for software or licenses to be considered "open source." This definition ensures that the principles of free access, modification, and distribution are upheld. Over time, a variety of open-source licenses have been created to cater to different needs and preferences. These licenses differ in terms of permissions, obligations, and restrictions.

Today, open-source licenses are widely used, fostering collaboration, innovation, and the sharing of knowledge in software development and beyond. They play a crucial role in shaping the open-source ecosystem and empowering individuals and organizations to create, share, and benefit from open-source software.

Over the course of its history, the open-source movement has witnessed the emergence of several open-source licenses tailored to accommodate diverse needs and preferences. Here, we will explore some of the prominent open-source licenses that have gained significant usage.

GNU General Public License v2 - (GPL)

The GNU General Public License (GPL) v2, released by the Free Software Foundation (FSF) in 1991, had a significant impact on open-source development. One of its key provisions is the copyleft provision. Under the copyleft provision, if you include a piece of software licensed under GPL v2 in your project, your project must also be licensed under GPL v2. This ensures that the open-source nature of the software is preserved, as any modifications or derivative works must be shared back with the community. In essence, the copyleft provision promotes collaboration and protects the principles of open-source software.

There is also GNU GPL V3 which can be found here.

Open Source Initiative -

GNU Lesser General Public License (LGPL) v2.1

The GNU Lesser General Public License (LGPL) v2.1 was released by FSF as an alternative to GNU GPL. It is designed to provide developers with more flexibility in using open-source libraries and components within their software. Is it similar to GPL that it is a copyleft license but it allows developers to use LGPL-licensed libraries without requiring the entire application to be licensed under LGPL. However, if you distribute the modified library, you must make the corresponding source code available for those modifications. The LGPL v2.1 is compatible with the GPL v2, which means that an LGPL-licensed library can be used in a GPL-licensed project. However, the reverse is not true GPL-licensed libraries cannot be used in an LGPL-licensed project.

The LGPL strikes a balance between allowing the use of open-source libraries in proprietary applications and preserving the open-source nature of the libraries themselves. It provides developers with the freedom to choose the licensing terms that best suit their needs when using and distributing software libraries.

Learn more about GNU LGPL v3 here.

Open Source Initiative -

GNU Affero General Public License (AGPL) v3

The GNU Affero General Public License (AGPL) v3 was created in 2007 by FSF as an extension of the GPL V3. The need for the AGPL arose due to the increasing popularity of web-based applications and the rise of the Software-as-a-Service (SaaS) model. It was specifically created to address the distribution of software over computer networks and to ensure that users have access to the corresponding source code. The AGPLv3 is compatible with the GPL v3. You can choose to license your software under either the GPL v3 or the AGPLv3, and you can combine code licensed under one with code licensed under the other.

If you make modifications to AGPL-licensed software, you are required to distribute those modifications under the terms of AGPLv3. Additionally, any derivative works based on AGPL-licensed software must also be licensed under AGPLv3.

Open Source Initiavtive -

Apache License 2.0

The Apache License 2.0 is a permissive license released by the Apache Software Foundation, it is considered one of the most business-friendly open-source licenses. It's classified as a permissive license which means it offers more freedom to users and developers compared to restrictive licenses GNU GPL. It allows you to use, modify, distribute, and sublicense the licensed software under certain conditions. One notable feature of the Apache License 2.0 is the patent grant. It explicitly grants users a patent license from the contributors of the software, ensuring that you the developer have the necessary rights to use the licensed software without the fear of patent infringement claims from the contributors. You are allowed to redistribute the licensed software under the Apache License 2.0. This includes both the original unmodified version and any modifications.

The Apache License 2.0 strikes a balance between permissive licensing and protecting the interests of contributors and users. It provides flexibility for developers and businesses while ensuring that proper credit is given to the original authors and maintaining the integrity of the licensed software.

Apache Org -

MIT License

The MIT License is recognized for its simplicity and permissive nature and is named after the Massachusetts Institute of Technology (MIT), where it was originally developed it grants users permission to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the licensed software. This means you have the freedom to modify the software according to your needs and distribute it, whether commercially or non-commercially and it includes a disclaimer of liability, stating that the software is provided "as is" without any warranty or guarantee of its performance or suitability for any purpose. The authors or copyright holders of the software are not liable for any damages or legal issues that may arise from the use or distribution of the software and the best thing is MIT License is compatible with other open-source licenses, allowing you to combine MIT-licensed code with code licensed under different open source licenses.

The MIT License is known for its simplicity and flexibility, making it a popular choice for open-source projects. It provides users with the freedom to use, modify, and distribute the software while maintaining clear attribution to the original authors.

Open Source Initiative -

Berkeley Software Distribution - (BSD)

The Berkeley Software Distribution - (BSD) originated from the University of California, Berkeley. It is considered a permissive license similar to Apache 2.0 and MIT License. It allows users to use, modify and distribute the licensed software. You are free to distribute the software under any license, including proprietary licenses, without any obligation to make your modifications publicly available. Most importantly BSD license includes a clause that states that the names of the original authors or contributors cannot be used to endorse or promote derivative works without their explicit permission. Similar to the MIT License, the BSD license includes a disclaimer of liability. It states that the software is provided "as is" without any warranty or guarantee of its performance or suitability for any purpose. The authors or copyright holders of the software are not liable for any damages or legal issues that may arise from the use or distribution of the software. There are different variations of the BSD license, such as the 2-clause (Simplified) BSD license and the 3-clause (Modified) BSD license. The variations mainly differ in the inclusion of an advertising clause, which required users to acknowledge the use of the software in their advertising materials.

The BSD license is known for its simplicity and permissive nature, allowing users to freely use, modify, and redistribute the licensed software. It has been widely adopted by various open-source projects, including the BSD operating systems themselves, as well as other software applications and libraries. The BSD license provides flexibility for both individual developers and commercial entities, making it a popular choice in the open-source community.

Open Source Initiative:
2 clause -
3 clause -


Open Source licenses play a significant role in the software development ecosystem as they empower individuals and organizations to share their software or creative works with the public. These licenses grant specific permissions to users while ensuring that certain rights and responsibilities are upheld.

They also serve as valuable resources for new developers, allowing them to learn and enhance their skills by accessing professional open source code without any cost. This enables them to contribute back to the community in the future, fostering a continuous cycle of learning and growth.

So, with the incorporation of appropriate licenses, happy coding! :)

Bonus Links

Learn more about OSI:

OSI Approved Licenses:

Confused about which license to choose?