Common Open Source Licenses: A Comprehensive Guide to Open Source Software Licensing

By Jeffrey D. Smith Last updated Aug 18, 2023

The adoption and use of open source software (OSS) has seen a significant surge in recent years. Organizations, both large and small, are increasingly turning to OSS as an alternative to proprietary solutions due to its cost-effectiveness, flexibility, and collaborative nature. However, the usage of OSS comes with certain legal implications that need to be carefully considered by developers and users alike. This article aims to provide a comprehensive guide on common open source licenses, highlighting their key features and discussing their impact on the development and distribution of OSS.

To illustrate the importance of understanding open source licenses, let us consider a hypothetical scenario where Company A decides to incorporate an open source library into their commercial product without fully comprehending the license terms associated with it. Unbeknownst to them, this particular license requires any modifications made to the library codebase to be released under the same license. As a result, when Company A starts distributing their product commercially, they inadvertently violate the licensing terms by not making their modifications available to others. This breach can lead to legal consequences such as lawsuits or demands for compliance from affected parties.

Given these potential pitfalls, having a clear understanding of different open source licenses is crucial for individuals and organizations involved in OSS development or utilization. By exploring various well By exploring various well-known open source licenses, developers and users can make informed decisions about the software they choose to incorporate into their projects. Some common open source licenses include:

GNU General Public License (GPL): This license is one of the most widely used open source licenses. It requires that any modifications or derivative works based on GPL-licensed software must be released under the same license. This ensures that the software remains freely available to the community.
MIT License: The MIT License is a permissive license that allows users to freely use, modify, distribute, and sublicense the licensed software. It requires minimal obligations and is often considered business-friendly.
Apache License 2.0: This license grants users extensive rights to use, modify, distribute, and sublicense the licensed software. It also includes patent clauses that provide additional protection against intellectual property claims.
BSD Licenses: There are several variants of the BSD License, including the simplified BSD License (also known as the 2-Clause BSD License) and the modified BSD License (also known as the 3-Clause BSD License). These licenses allow for both commercial and non-commercial use of the licensed software with relatively few restrictions.
Creative Commons Licenses: While primarily used for creative works like images and music, certain Creative Commons licenses can also be applied to software. These licenses offer different levels of permissions and restrictions, allowing creators to define how their work can be shared or adapted.

Understanding these licenses involves carefully reading their terms and conditions to ensure compliance with their requirements. Developers should also consider potential dependencies on other open source libraries or components which may have different licensing terms.

In addition to understanding specific licenses, developers should also be aware of best practices for managing OSS within their projects. This includes keeping track of all third-party libraries used in a project, documenting license information for each library, respecting copyright notices, providing attribution where required, and complying with any additional obligations specified by the licenses.

By being knowledgeable about open source licenses and adhering to their requirements, developers and users can navigate the legal implications of OSS effectively while benefiting from the advantages it offers.

GNU General Public License (GPL)

Imagine a software developer named John who has created a new and innovative software application. He wants to share his creation with the world while ensuring that it remains accessible for others to use, modify, and distribute freely. In this scenario, the GNU General Public License (GPL) becomes an important consideration for John.

The GPL is one of the most widely used open source licenses, designed by Richard Stallman in 1989 for the GNU Project. Its primary objective is to guarantee users’ freedom to access, modify, and distribute software under certain conditions. One key feature of the GPL is its copyleft provision, which requires any derivative works or modifications based on GPL-licensed software to be released under the same license terms.

To better understand how the GPL operates and impacts both developers and users alike, let us consider some essential aspects:

Copyleft Provision: The heart of the GPL lies in its copyleft provision. It ensures that anyone who modifies or extends a piece of software licensed under the GPL must make their changes available as free software under identical licensing terms. This fosters collaboration and encourages contributors to give back to the community.
Distribution Requirements: When distributing software under the GPL, whether modified versions or original creations, there are specific obligations that must be met. These include providing access to the complete corresponding source code along with clear instructions on accessing and modifying it.
Compatibility Concerns: While promoting openness and collaboration among developers, compatibility issues can arise when combining different projects licensed under various open source licenses. Understanding these complexities becomes crucial when considering integrating or deriving work from multiple sources governed by diverse licenses.
Legal Implications: Complying with the requirements set forth by the GPL is not only ethically significant but also holds legal implications for developers who choose this license for their projects. Violations could result in potential litigation or loss of reputation within the open source community, emphasizing the importance of understanding and adhering to the license terms.

By delving into these key aspects, one gains a deeper appreciation for the unique characteristics of the GPL. In the subsequent section, we will explore another popular open source license known as the MIT License and examine its distinctive features in comparison to the GPL.

MIT License

GNU General Public License (GPL) is one of the most widely used open source licenses, promoting software freedom and collaboration. Let’s now explore another popular license in the open source community: the MIT License.

The MIT License provides developers with a permissive licensing option that enables them to freely use, modify, distribute, or sell their software. Unlike the GPL, which focuses on copyleft principles and requires derived works to be licensed under the same terms, the MIT License allows for greater flexibility by not imposing such restrictions. This license has gained popularity due to its simplicity and compatibility with both commercial and non-commercial projects.

To illustrate how the MIT License can benefit developers, let’s consider a hypothetical scenario where a developer creates an innovative photo editing software called “SnapPro.” By releasing SnapPro under the MIT License, the developer grants users permission to freely download, modify, and redistribute their application without any legal barriers. This fosters collaboration within the development community while allowing individuals or organizations to incorporate SnapPro into their own projects seamlessly.

Notably, when choosing between different open source licenses like GPL or MIT, it is important to consider factors such as project goals and desired levels of control. Here are some key points highlighting why developers might opt for the MIT License:

Flexibility: The permissive nature of this license allows for easier integration with proprietary software.
Commercial viability: Companies seeking to build upon existing open source projects may prefer this license since there are no requirements for making derivative works available under similar terms.
Community adoption: Many well-known projects have adopted the MIT License over time, creating a robust ecosystem around this licensing model.
Innovation potential: Developers who prioritize widespread usage and contributions from others may choose this license as it encourages collaborative development.

	GNU General Public License (GPL)	MIT License
1.	Focuses on copyleft principles	Provides permissive licensing
2.	Requires derived works to be licensed under the same terms	Allows for greater flexibility and no such restrictions
3.	Preferred by projects that promote software freedom and collaboration	Attracts developers seeking simplicity, compatibility, and commercial viability

Moving forward, we will explore another popular open source license: the Apache License. This license offers a unique approach that balances openness with certain patent protections, ensuring both collaborative development and legal safeguards.

Apache License

Continuing our exploration of common open source licenses, we now delve into the GNU General Public License (GPL). This copyleft license, developed by Richard Stallman and the Free Software Foundation (FSF), aims to protect users’ freedom by ensuring that derivative works based on GPL-licensed software remain free and open-source. Let’s examine the key characteristics and implications of this widely used license.

Example: Consider a hypothetical scenario where a software developer named Alex creates an innovative tool using code released under the GNU GPL. As per the terms of this license, Alex must make their entire codebase available as open source when distributing or modifying their tool. However, it also means that any derived work built upon Alex’s tool will have to adhere to the same licensing requirements, thus preserving its openness for future developers.

To gain a better understanding of how the GPL operates within the realm of open source software licensing, let us explore its notable features:

Copyleft Provision: The GNU GPL is known for its strong copyleft provision, which ensures that anyone who distributes or modifies GPL-licensed software must do so under the same license. Consequently, all subsequent versions or derivative works retain their open-source nature.
Source Code Availability: One of the core principles behind the GPL is guaranteeing access to source code. Users receiving software governed by this license are entitled to obtain and modify its underlying code freely.
Compatibility with Other Licenses: While compatibility may vary among different licenses, it is worth noting that some incompatibilities exist between certain versions of the GPL and other licenses—particularly those with more permissive clauses.

Let’s summarize these aspects in a concise table format:

Features	Description
Copyleft Provision	Requires distribution or modification of licensed software under the same GPL license conditions; preserves openness through derivative works.
Source Code Availability	Ensures users have access to the source code of GPL-licensed software, enabling them to modify and understand its inner workings.
Compatibility	While the GPL may not be compatible with all licenses, it is important for developers to assess compatibility when considering incorporating or modifying GPL-licensed software within their projects. Careful evaluation helps maintain licensing compliance and freedom.

BSD Licenses are another category of open-source licenses that offer distinct characteristics in comparison to the GNU General Public License.

In this way, we transition into our subsequent section about “BSD Licenses,” where we will explore yet another widely used family of open source licenses.

BSD Licenses

Transitioning from the previous section on the Apache License, we now move on to explore another popular open source license known as the GNU General Public License (GPL). To illustrate its application, let us consider a hypothetical scenario where a software developer creates a new web browser and decides to release it under the GPL.

The GNU General Public License is one of the most widely used open source licenses. Its primary aim is to ensure that users have the freedom to view, modify, and distribute the software while guaranteeing that any derivative works remain open source. Here are some key characteristics of this license:

Copyleft Provision: The GPL employs a copyleft provision which requires anyone who distributes or modifies software licensed under it to also make their modifications available under the same terms. This approach ensures that subsequent versions or derivatives of the software continue to be freely accessible.
Protects User Freedom: By placing restrictions on proprietary distribution and modification of code, the GPL seeks to safeguard user freedoms by preventing closed-source exploitation.
Strong Community Support: The GPL has fostered robust communities around many successful projects such as Linux and Git. These communities actively contribute enhancements and bug fixes back into the project pool for everyone’s benefit.
Compatibility Considerations: It should be noted that compatibility can sometimes be an issue when combining GPL-licensed code with other licenses. Before integrating GPL components into your project, you must carefully evaluate potential conflicts.

To further understand how different open source licenses compare against each other, Table 1 presents a simplified comparison between three common licenses – Apache License, BSD Licenses, and GNU General Public License based on factors like permissiveness, copyleft provisions, and commercial usage limitations.

	Permissive	Copyleft Provisions	Commercial Usage Limitation
Apache	Yes	No	No
BSD	Yes	No	No
GPL	No	Yes	Yes

By exploring its features and provisions, we can gain a comprehensive understanding of the varied choices available to developers when it comes to selecting an appropriate license for their software projects.

Eclipse Public License

In the previous section, we explored the BSD licenses and their implications for open source software. Now, let us delve into another widely used open source license: the Eclipse Public License (EPL). To illustrate its relevance, consider a hypothetical scenario where a team of developers is working on an innovative web application called “WebPlex.” They decide to release WebPlex under the EPL to encourage collaboration and foster community involvement.

The EPL is known for its flexibility and compatibility with other licenses. Here are some key features:

Copyleft Provision: Like many open source licenses, the EPL includes a copyleft provision that ensures derivative works or modifications of the original code must also be released under the same license.
Commercial Use: The EPL allows commercial use of software licensed under it without imposing additional restrictions. This aspect makes it attractive for businesses seeking to leverage open source projects in their proprietary products or services.
Compatibility with Other Open Source Licenses: The EPL is compatible with various other open source licenses such as Apache License 2.0, GPL v3, and LGPL v3. This compatibility facilitates collaborative development across different licensing frameworks.
Community Engagement: By using the EPL, developers can benefit from active participation in diverse communities centered around shared values and goals.

To further understand how the EPL compares to other prominent open source licenses, take a look at this comparison table:

	Copyleft Provision	Commercial Use	Compatibility	Community Engagement
Eclipse Public License (EPL)	Yes	Yes	High	Active
Apache License 2.0	No	Yes	Moderate	Engaged
GNU General Public License (GPL) v3	Yes	No	High	Diverse

This table highlights the unique characteristics of each license and showcases how the EPL stands out in terms of copyleft provisions, commercial use permissions, compatibility with other licenses, and community engagement.

Moving forward, we will explore another significant open source license: the Mozilla Public License (MPL). This license is particularly notable for its approach to handling modifications and distributing software. Let us delve into the MPL and examine its implications for open source development.

Mozilla Public License (MPL)

Building upon our discussion of the Eclipse Public License (EPL), we now turn our attention to another prominent open source license, namely the Mozilla Public License (MPL).

The Mozilla Public License (MPL) is an open source software license that was developed by the Mozilla Foundation. It is primarily used for distributing and licensing free and open-source software. Similar to the EPL, MPL allows users to modify, distribute, and use the licensed software under certain conditions.

One example of a project that utilizes the Mozilla Public License is the web browser Firefox. Released in 2004, Firefox has become one of the most popular alternatives to mainstream browsers. The MPL has enabled developers from around the world to contribute their expertise towards improving this open-source browser, resulting in constant updates and enhancements.

Provides freedom for users to modify and customize software according to their needs.
Encourages collaboration among developers through its permissive nature.
Offers protection against patent claims, ensuring a secure development environment.
Enables commercial exploitation while maintaining access to source code.

Advantages	Disadvantages	Considerations
Encourages innovation	Requires attribution	Compatibility concerns
Allows commercial use	May introduce legal risks	Community engagement
Protects against patents	Limited control over changes	Licensing obligations
Promotes transparency	Potential fragmentation	Security vulnerabilities

In summary, the Mozilla Public License provides a framework for promoting collaboration and innovation within the realm of open-source software. By allowing modifications while protecting against potential legal issues, it strikes a balance between openness and stability. Developers can benefit from its flexibility, as demonstrated by projects such as Firefox. However, it’s important to consider compatibility concerns when utilizing MPL-licensed software and ensure compliance with any licensing obligations.