What Is Open Source Software Licensing?

Key takeaways

Open source software licensing protects the software developer’s intellectual property and defines when and how people can use it. Here are some important facts to know: 

• Open source software use is growing, with 95 percent of surveyed open source software users maintaining or increasing their use of it from 2023 to 2024 [1].

• Permissive open source software licenses provide the broadest rights to use, modify, and distribute the software, while copyleft licenses may require applying the original license to any modified source code.

• You can comply with open source licensing requirements as a software developer by providing proper attribution, documenting any changes, and establishing an organization-wide compliance policy. 

Learn more about open source software licensing, why it’s useful, what types you can use, and how to comply with open source software licenses. If you aspire to create your own open source software, consider enrolling in the IBM Back-End Development Professional Certificate. You’ll have the chance to learn how to write back-end applications with object-oriented programming languages in as little as six months.

What is open source software licensing?

Open source software licensing permits you to use open source software, which is free and open to the public, and dictates how you can inspect, distribute, and modify it. Developers can distribute their software under terms established by the license, which may state how other users can modify the source code. 

In 1998, the Open Source Initiative (OSI) launched, coined the term “open source,” and began issuing open source software licenses [2]. Elements of an open source license, as defined by OSI, include [2]:

• Users can distribute the software for free, without paying a royalty.

• Users must have access to the software and its source code.

• Users must be able to modify the source code.

• The license may not discriminate against individuals, groups, or specific fields. 

Many variations of open source software licenses exist, and software developers have the freedom to design a license that adheres to the terms they desire.

Why licensing is important in open source projects

Open source software licensing is important because it protects the intellectual property of the software developers. It gives software developers control of their project, allowing them to distribute it under terms that they define. A license for open source software also holds organizations accountable, ensuring they comply with the distribution, modification, and use guidelines established by the license. In doing so, organizations protect themselves against non-compliance issues that may result in restrictions on a software’s use or lawsuits for not adhering to established guidelines. 

Open source licenses also foster innovation and collaboration. Programmers and software developers from across the globe can collaborate on a project, optimizing it and potentially making it more effective. Moreover, these licenses dictate how users can modify the source code to suit their needs, making the software adaptable, flexible, and practical for more organizations. 

Who uses open source software licensing?

Individuals and organizations across industries rely on open source software licensing. Many tech-focused industries, such as cloud computing, artificial intelligence, and robotics, rely on open source software. Additionally, health care, agriculture, and scientific research organizations may also benefit from the use of open source software.

Open source software license types and comparisons

Hundreds of open source software licenses exist, giving developers the opportunity to select one with the permissions and restrictions they desire. However, these licenses generally fall into two categories: permissive and copyleft.

Permissive licenses

Permissive licenses provide the broadest rights, giving you complete freedom to use, modify, and distribute the software. Some permissive licenses even give you the opportunity to sell copies of the software, as long as you list the original copyright. As a result, open source software with a permissive license is ideal if you want to develop your own software and use elements of an open source software in it. 

Popular examples of permissive licenses include:

• MIT License: A popular, simple license allowing you to reuse the source code for any purpose, with the only stipulation being that you include a copyright notice when distributing it

• Apache License: A license offering similar permissions as the MIT license, but requiring you to credit the original source code and provide a detailed list of any modifications

• Berkeley Source Distribution (BSD) Licenses: Two-, three-, and four-clause (BSD) licenses with varying levels of restrictions related to naming the original authors without prior permission and releasing the original authors from any liability

Copyleft licenses

Copyleft licenses require you to distribute any modifications you make to the source code under the same license as the original code. You can find both strong and weak copyleft licenses, depending on the level of restrictiveness you prefer. Strong copyleft licenses require you to apply the same license to all of your source code. Weak copyleft licenses only require you to apply that license to the original source code, while your modifications may adhere to a different license. 

Some examples of copyleft left licenses include:

• GNU General Public License: A popular, strong copyleft license requiring you to distribute your source code, including modifications, under the original license

• Eclipse Public License: A weak copyleft license offering more freedom in integrating code into proprietary software, making it a popular choice for business software

• Mozilla Public License: The least restrictive copyleft license, allowing you to use the source code in any closed-source or proprietary software, provided that you keep it in separate files and distribute them with the software release

How to comply with open source software licenses

Compliance with open source software licenses is crucial, protecting you from legal consequences, financial penalties, or security risks associated with non-compliance. Understanding the specific requirements of the open source software you’re using is essential to ensure proper compliance. Pay attention to the following licensing requirements as you use or repurpose open source software.

Provide proper attribution.

Review the license to ensure you provide proper attribution to the open source software. This attribution may include listing a copyright notice or the original license text with your modified source code.

Confirm source code availability.

Copyleft licenses require you to make the source code available. Check the terms of the copyleft license to determine what you need to make available, including your modifications.

Document changes as required.

If the open source software license requires you to document or publish modifications, you’ll need to keep track of those changes as you revise the source code. 

Use the proper license.

Copyleft licenses require all or part of the source code to fall under its original license. Review the specific details of the open source license to ensure you properly license your source code.

Establish a compliance policy.

At the organizational level, develop a policy detailing what open source software licenses developers should use, and establish steps to verify that license requirements are followed. Outline any automated tools for developers to manage open source software usage and ensure compliance.

What are the four types of software licenses?

The four software license types are perpetual, subscription, proprietary, and open source. Perpetual licenses allow you to use the software program indefinitely after a one-time purchase. Subscription licenses, often known as software as a service (SaaS), require a monthly or annual fee to access the software and include regular software updates. Organizations holding a proprietary software license create and maintain the software, without sharing the code with users. This type of license contrasts with open source licensing, which allows you to access, modify, and distribute the source code.

Read more: What Is Software as a Service? Definition and Examples

Tools for open source license management

Ninety-five percent of open source software users reported maintaining or increasing their use of it, according to the 2024 State of Open Source Report [1]. As individuals and organizations increasingly access open source software, proper license management is imperative, and open source license management tools can streamline the process of documenting changes and ensuring license compliance. 

Open source license management solutions can automate the following processes:

• Scanning and identifying license requirements

• Identifying vulnerabilities in your source code

• Developing a central repository for artifacts

• Generating automated attribution notices per license requirements

• Flagging any licenses that may present legal issues

Choose from commercially available solutions and open source options that can help you manage your open source licensing documentation and compliance. A few of these options include:

• FOSSA: Automated license scanning, policy enforcement, and attribution

• Synk: Software composition analysis to enhance risk management

• Sonatype: Software supply chain security, including vulnerability protection and open source risk management

• OSS Review Toolkit: Software composition analysis, vulnerability management, and license compliance

Stay informed of software industry trends

Subscribe to our weekly LinkedIn newsletter, Career Chat, for career trends and tips. Then, check out these resources for additional guidance:

• Watch on YouTube: How to Become a Software Developer

• Learn programming: Python Syntax Cheat Sheet

• Read an insider story: How One Software Developer’s Leadership Aspirations Led Her to Graduate School

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