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What is an Open-Source License?

What is an Open-Source License?

By Ani Ghazaryan
8 min readApril 21, 2023

It's been a while since shelling out big bucks for proprietary software has ceased being cool. Who likes paying exorbitant fees for software, anyway? Especially now, when open-source solutions have become music to developers' ears as a cost-effective, flexible, and transparent alternative to proprietary software solutions. Though with great power comes great responsibility. The need for legal frameworks to govern the use of software and distribution has never been this pressing — a perfect time to get to know about open-source licenses.

In this article, we will delve into what open-source licenses are, why they matter, and we will go through the various license types available. Whether you're a developer, a business owner, or simply curious about the world of open source, this blog post will provide you with the knowledge you need to navigate the open-source landscape.

Defining open-source licenses

An open-source license is a legal agreement that allows users to access, modify, and distribute a piece of software's source code. This type of license is based on the principles of the open-source movement, which emphasizes collaboration, transparency, and community-driven development. Typically, it grants users the following rights:

  • The right to access and use the software's open-source code.
  • The right to modify the software's source code.
  • The right to distribute the software's source code and any modified versions.

These rights are often subject to certain conditions, such as giving credit to the original author or contributing any modifications back to the community.

Why use open-source software licenses?

What makes open-source licenses a common choice is the legal foundation: they provide a legal framework that enables developers to collaborate and share their work without fear of litigation. Without these licenses, it would be difficult for developers to work together on open-source projects, and the world would have been devoid of as many valuable innovations as there exist today.

Additionally, open-source software licenses help prevent software from becoming monopolized by a single entity. By allowing users to modify the source code, open-source licenses ensure accessibility across the web.

Open source licenses in practice

Copyleft and permissive licenses are the two categories of open-source licenses, which differ in their approach to licensing and distribution of software.

Copyleft open-source licenses

Copyleft licenses require any derivative works or modifications to the software to be released under the same license as the original software. This means that if you modify or build upon the original software, you must also release your work as open-source under the same copyleft license. Examples of copyleft licenses include the following:


GPL logo

The GNU General Public License (GPL) is an open-source license used by developers all over the world. Created by the Free Software Foundation, the license ensures that any software developed under it remains freely accessible and modifiable by anyone. It has been used in countless software projects, from web browsers to operating systems, and has become a cornerstone of the open-source movement. The GPL license empowers developers to collaborate and innovate without worrying about proprietary restrictions or licensing fees.


AGPL logo

Being a variant of the GPL, Affero General Public License (AGPL) is specifically designed for software distributed over a network. Similar to GPL, the AGPL license ensures that any changes made to the software by users are made available to the public. The AGPL has been used in applications such as online games and social media platforms, helping maintain the open and collaborative nature of those tools.


LGPL logo

The Lesser General Public License (LGPL) is another open-source license that allows for the use of open-source software in proprietary applications. The LGPL is a popular choice for developers who want to use open-source libraries and frameworks without releasing their entire application under an open-source license.


EPL logo

This permissive open-source license is designed to be compatible with other open-source licenses. Created by the Eclipse Foundation, the Eclipse Public License (EPL) has become a popular choice for developers who want to combine code from multiple open-source projects. The license includes a patent license which ensures that any associated patents are licensed for free and open use.


MPL logo

As a hybrid open-source license, the Mozilla Public License (MPL) combines elements of both the GPL and the BSD license. Created by the Mozilla Foundation, the MPL allows for the use of open-source software in proprietary applications while also requiring any modifications to the software to be made available under the same license. This has made the MPL a hot target for open-source software that is distributed as part of a larger commercial product. Overall, all of these licenses have helped to foster a culture of collaboration and innovation in the technology industry. Yet copyleft licenses are only one side of the coin.

Permissive open-source licenses

Permissive licenses allow anyone to use, modify, and distribute the software without any requirement to release derivative works as open-source. They give developers more freedom to use the software in their own projects, even if those projects are proprietary. The key difference between copyleft and permissive licenses lies in the degree of control that they offer: While copyleft licenses ensure that any modifications or additions made to the software remain open-source, permissive licenses allow developers to incorporate the software into their own projects, whether they're open-source or proprietary. Some of the common permissive licenses include:


Apache logo

Apache License, the king of permissive licenses, is designed to be flexible and easy to use, allowing users to modify, distribute, and use the software without any restrictions. It also includes a patent license, which provides additional protection for users against potential patent infringement claims. Often used for web and cloud-based projects, Apache's flexibility makes it an incredibly popular choice in the developer community.


MIT logo

Next is the MIT License, just as widely used in the open-source community. It is a simple and straightforward license that allows users to use, modify, and distribute the software without constraints. As you may have guessed, the MIT license is a popular choice for academic and research projects, as well as for smaller software projects.


BSD logo

The BSD License is another family of permissive open-source licenses that are commonly used in academic and research settings, and it does not require any derivative works to be released as open-source. The BSD license lends itself well to networking and server software, as well as operating systems and research projects.


Unilicense logo

Finally, there's the Unilicense, which is a permissive license designed to be as simple and easy to use as possible. It does not include any warranty or liability provisions and is mostly opted for smaller-size personal or hobby projects

At the end of the day, the choice of which license to use will depend on the specific needs and requirements of your project. By understanding the benefits of each license, you can make an informed decision that will help you achieve your goals and contribute to the open-source community. One last thing to keep in mind before we wrap up.

License compatibility

When using open-source software, license compatibility has to be a crucial consideration, as different licenses may have conflicting terms or requirements. And here is what compatibility means in the open-source-software-licenses context:

License compatibility refers to the ability of two or more open-source licenses to coexist and be combined in a single software project. When two licenses are compatible, it means that code released under one license can be incorporated into a project that uses another compatible license. For example, the Apache license and the MIT license are both permissive licenses and are considered compatible with each other, meaning the code released under the Apache can be incorporated into a project that uses the MIT license and vice versa.

However, not all licenses are compatible with each other. Some licenses have stricter requirements than others and can impose few restrictions on how the software can be utilized and distributed. For instance, the GPL is a copyleft license, which means that if you incorporate code released under the GPL into your project, your project must also be released under the GPL. This makes the GPL incompatible with some permissive licenses, such as Apache or BSD.

When combining code from different open-source licenses, make sure to carefully review the terms of each license to ensure that they are compatible. In some cases, it may be necessary to obtain permission from the original author or seek legal advice.

Wrap up

Open-source licenses are an axis for the open-source software ecosystem. By providing a legal framework for collaboration and innovation, these licenses have enabled developers around the world to work together on groundbreaking projects.

Whether you're a developer, a business owner, or simply an enthusiast, understanding the ins and outs of open-source licensing can give you an edge in navigating the rapidly evolving world of technology.

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