Choosing an open-source license for your software project is a critical decision that can significantly impact its use, modification, and distribution. When you select an open-source license, you define the terms under which others can use your software. This decision impacts how freely others can use your code and how modifications and redistributions are handled. However, making the wrong choice can lead to legal challenges and restrict the intended use of your software, potentially causing significant setbacks to your project.

Key Points

  • Regulating Software Use with Open Source Licenses: Open source licenses are essential for managing software use, modification, and distribution. They strike a balance between granting freedom to users and protecting the rights of creators. Common licenses include GPL, MIT, Apache, and Creative Commons.
  • Types of Open Source Licenses: Open source licenses fall into several categories: permissive, weak copyleft, strong copyleft, Public Domain, Source Available, and Academic. Permissive licenses offer more freedom and fewer obligations, while copyleft licenses require stricter terms. Source Available licenses allow the source code to be viewed and modified but may impose some restrictions. Academic licenses are often used for educational and research purposes, allowing free use and distribution within academic contexts while potentially restricting commercial use.
  • Ensuring Compliance: Complying with open source licenses demands careful management practices. These include proper attribution, distributing source code for modifications, and regularly reviewing licensing terms because the licenses can and do change over time.

Common Open Source Licenses and Their Impact on Software Development

GNU General Public License (GPL), MIT License, Apache License, and Creative Commons License are among the most widely used open-source licenses. These licenses establish clear guidelines and restrictions on how software can be used, modified, and shared, ensuring that the principles of open source are maintained while protecting the rights of the original creators.

These licenses play a subtle but significant role in shaping the software supply chain. They dictate the terms under which code can be altered and redistributed, influencing the selection and integration of open-source components. This, in turn, affects the development trajectory of software projects and the strategies used to ensure compliance and security.

These licenses control permissible modifications and set rules for adapting and sharing open-source code. For example, the GPL requires that any modified software versions be distributed under the same license, ensuring the modified code remains open source. Permissive licenses like MIT and Apache allow for more flexibility, enabling integration with proprietary software.

Access to open-source code is invaluable for troubleshooting and understanding software functionality, especially in cases where documentation is incomplete or incorrect. This transparency allows developers to diagnose and fix issues more effectively, contributing to the robustness and reliability of open-source projects.


Permissive Licenses Explained

Permissive licenses allow users extensive freedom to use, modify, and distribute the software with minimal restrictions. They require minimal obligations, typically including the original copyright notice and license terms in all copies or substantial portions of the software and documentation.


  • Modifications Must Be Open: Modifications to the original code must be released under the same weak copyleft license.

  • Linking Flexibility: Allows linking with proprietary code without requiring the proprietary code to be open-sourced.

  • Dual Licensing: In some cases, weak copyleft licenses can be combined with other licenses, offering more flexibility for developers.


Examples of Permissive Licenses

MIT License: Simple, highly permissive. Users can freely use, modify, and distribute software if the original copyright notice and license terms are included.

Apache License 2.0: Comprehensive, allows for the distribution of derivative works and modifications under different licensing terms. Includes a patent grant.

BSD License: Simple and free, with variations that may include additional terms. Users can use, modify, and redistribute software with the original copyright notice and license included.


Benefits of Permissive Licenses

  • Flexibility: Developers can use, modify, and distribute software with minimal restrictions.

  • Encourages Innovation: Reduces barriers to adoption and contribution, fostering a collaborative environment.

  • Broad Adoption: It is easy to comply with, making it attractive for a wide range of projects, including commercial ones.

  • Legal Simplicity: Minimal legal obligations make it easy to understand and use, reducing overhead for developers and organizations.

Use Cases for Permissive Licenses

  • Open Source Projects: Ideal for projects encouraging broad adoption and contribution without imposing significant restrictions.

  • Commercial Integration: Suitable for businesses that want to integrate open-source components into proprietary software without complex licensing requirements.

  • Academic Research: Commonly used in academic settings where researchers want to share their work freely and encourage further innovation and collaboration.

  • Rapid Development: Useful for startups and tech companies that need to iterate quickly and leverage existing open-source solutions without legal complexity.

Examples of Companies Using Permissive Licenses

Facebook uses the MIT License for several of its open-source projects, one of the most notable being React, a widely-used JavaScript library for building user interfaces. The MIT License allows developers to freely use, modify, and distribute React in open-source or proprietary projects.

AWS uses Apache License 2.0 for several of its open-source projects, with one prominent example being Apache Hadoop, an open-source software framework used for distributed storage and processing of large data sets. AWS contributes to and utilizes Apache Hadoop within its cloud services, particularly in Amazon EMR (Elastic MapReduce).

Google uses the BSD license for many of its open-source projects, one of the most notable being the BoringSSL library, a fork of OpenSSL designed to meet Google’s needs. BoringSSL is used in Google’s servers and also in the Chrome web browser. The BSD license allows Google to freely modify and distribute BoringSSL while giving others the same freedom.


Threatrix automates the annotation requirements for permissive licenses by automatically detecting and identifying the licensing requirements of open-source components during the build process, saving developers time and effort while maintaining compliance


Copyleft Weak Licenses Explained

Copyleft weak licenses, also known as “weak copyleft” licenses, are a category of open-source licenses that strike a balance between permissive and strong ones. They allow the code to be freely used, modified, and distributed, but with certain conditions that ensure derivative works remain open source under the same license. However, these conditions are less stringent than strong copyleft licenses, allowing some proprietary use under specific circumstances.


  • Modifications Must Be Open: Modifications to the original code must be released under the same weak copyleft license.
  • Linking Flexibility: Allows linking with proprietary code without requiring the proprietary code to be open-sourced.
  • Dual Licensing: In some cases, weak copyleft licenses can be combined with other licenses, offering more flexibility for developers.


Examples of Weak Copyleft Licenses

GNU Lesser General Public License (LGPL): This license allows the use of licensed code within proprietary software as long as any modifications to the LGPL-licensed code are released under the LGPL.

Mozilla Public License (MPL): It requires modifications to MPL-licensed files to be open-sourced but allows these files to be combined with proprietary code without affecting the proprietary code’s license.

Common Development and Distribution License (CDDL): Similar to MPL, modifications to CDDL-licensed files must be made available under the same license but allow combining with proprietary code.


Benefits of Weak Copyleft Licenses:

  • Encourages Use in Proprietary Software: Allowing proprietary software to link with open-source components without requiring the entire software to be open-sourced encourages more widespread use of open-source code.

  • Maintains Open-Source Integrity: Ensures that improvements and modifications to the open-source components remain open, contributing back to the community.


Use Cases for Copyleft Weak Licenses

Copyleft weak licenses are ideal for developing libraries and frameworks for widespread use. These licenses ensure that improvements to the library or framework are shared with the community without imposing open-source obligations on the entire application that uses the library.

Examples of Companies Using Copyleft Weak Licenses 

  • Red Hat develops and maintains several high-performance data processing libraries under the LGPL. One notable example is GStreamer, a powerful multimedia framework for creating streaming media applications. GStreamer is licensed under the LGPL, allowing developers to use it in their proprietary applications without the obligation to open-source their entire codebase. However, any modifications to the GStreamer library itself must be shared under the same LGPL license.

Plugins and Extensions

When developing plugins or extensions for larger applications, copyleft weak licenses allow the plugins to be open-source while maintaining the main application’s proprietary status.

  • OpenSceneGraph is an open-source, high-performance 3D graphics toolkit licensed under the Mozilla Public License (MPL). While OpenSceneGraph is open-source, it can be used to create plugins for proprietary graphics software. This means the core proprietary software remains closed-source, but any modifications to the OpenSceneGraph-based plugins must be shared under the MPL.

Enterprise Software Integration

Enterprises often use a mix of open-source and proprietary software. Copyleft weak licenses enable them to integrate open-source components without risking the exposure of proprietary code.

  • MariaDB is an LGPL-licensed fork of MySQL, widely used as an open-source database engine. Enterprises can integrate MariaDB into their proprietary software solutions, benefiting from its robust and efficient database management capabilities. While MariaDB remains open-source and any modifications to the database engine must be shared with the community, the proprietary applications that use MariaDB do not have to disclose their source code.

Academic and Research Projects

Copyleft weak licenses are suitable for academic and research projects that benefit from collaborative development and wide dissemination while protecting specific innovations or applications derived from the project.

  • SciPy, a Python-based ecosystem of open-source software for mathematics, science, and engineering, includes a library licensed under the Lesser General Public License (LGPL). This licensing choice allows other researchers and developers to use and improve the library while ensuring that any enhancements remain open-source.

Open Source Business Models

Companies that offer dual-licensing models often use copyleft-weak licenses for their open-source versions. This approach allows them to offer an open-source version under a weak copyleft license while providing a proprietary version with additional features or support.

  • Mozilla Corporation, known for its web browser Firefox, uses the Mozilla Public License (MPL) for several projects. One notable example is the Mozilla Firefox web browser, which is available as open-source under the MPL. While the core browser is open-source, Mozilla offers additional services and features through its commercial offerings, such as Firefox for Enterprise, which includes extended support and deployment options tailored for business environments.

Government and Public Sector Projects

Governments and public sector organizations can use copyleft weak licenses to promote transparency and collaboration while integrating open-source components with proprietary systems.

  • Project Open Data, initiated by the White House, includes tools and resources to improve data transparency and accessibility. One of the tools developed under this initiative is the Project Open Data Dashboard, licensed under the Mozilla Public License (MPL).


Strong Copyleft Licenses

Strong copyleft licenses are open-source licenses that ensure that any derivative works of the software are also distributed under the same license terms. This means that modifications to the software and any software that incorporates it must be open-sourced under the same license. Strong copyleft licenses are ideal for projects that aim to guarantee software freedom and prevent proprietary forks.


  • Mandatory Sharing: Modifications and derivative works must be released under the same license.
  • Source Code Availability: The source code must be made available when distributing the software.
  • Propagation: The copyleft license applies to all derivative works, ensuring they remain free and open-source.


Examples of Strong Copyleft Licenses

GNU General Public License (GPL) Versions (GPLv2 GPLv3): requires that any modified versions of the software be distributed under the GPL. It also requires that the software’s source code be made available to users and prohibits the incorporation of the software into proprietary software.

Affero General Public License (AGPL) Versions (AGPLv1 AGPLv3): requires the source code to be made available to users who interact with the software over the network, ensuring that modifications and improvements are shared with the community.

The Linux kernel is licensed under the GPL, ensuring that all modifications and distributions of the kernel remain open-source. This has contributed to its widespread adoption and collaborative development.


Use Cases for Strong Copyleft Licenses

Strong copyleft licenses benefit large, collaborative projects by ensuring all contributions remain open-source. This fosters an environment where developers can freely share and improve each other’s work.

  • The GNU Compiler Collection (GCC) is licensed under the GPL, allowing developers to contribute to and enhance the compiler while ensuring that all improvements remain freely available.

Web Applications and Network Software

For web applications and network software, the AGPL extends the principles of the GPL to include software accessed over a network. This ensures that users interacting with the software over the internet can access the source code.

  • Nextcloud, a file-sharing and collaboration platform, uses the AGPL to ensure users can access the source code, even when the software is used over a network.

Educational and Research Software

Educational and research institutions often use strong copyleft licenses to ensure their software and research tools remain open and accessible to the academic community. This promotes transparency, reproducibility, and collaboration in research.

  • The R Project for Statistical Computing, developed by the R Foundation, is an example of a research team using the GPL license. R is a free software environment for statistical computing and graphics widely used by statisticians and data scientists.

Public Sector and Government Projects

Governments and public sector organizations use strong copyleft licenses to promote transparency and accountability in software development. Making their software open-source ensures that the public can access and verify the code.

  • DHIS2 (District Health Information Software 2) is an open-source public health monitoring tool licensed under the GNU General Public License (GPL). It is widely used by government agencies and organizations worldwide to collect, manage, and analyze health data. By releasing DHIS2 under the GPL, the University of Oslo ensures that the software remains open-source and that any improvements made by other agencies or organizations are shared back with the community.

Commercial Software with a Dual-Licensing Model

Some companies use strong copyleft licenses for their open-source versions while offering a proprietary license for commercial use. This dual-licensing model allows them to benefit from community contributions while generating revenue from commercial licenses.

  • MySQL, a widely used open-source relational database management system, has successfully employed a dual-licensing model. MySQL is released under the GNU General Public License (GPL), encouraging community development and contributions. At the same time, the company offers a commercial license for businesses that do not comply with the GPL’s terms, providing them with additional features, support, and the flexibility to integrate MySQL into their proprietary software without the obligation to open-source their code. This dual-licensing approach has allowed MySQL to benefit from the contributions of the open-source community while also generating revenue from businesses that require a commercial license. This model has contributed to MySQL’s widespread adoption and success in open-source and commercial markets.

Benefits of Strong Copyleft Licenses

  • Ensures Freedom and Openness: Strong copyleft licenses ensure that the software and its modifications remain open and free for all users by requiring that derivative works remain under the same license.

  • Promotes Collaboration and Sharing: Developers are encouraged to share their improvements and modifications, fostering a collaborative environment and contributing back to the community.

  • Protects Against Proprietary Forks: Strong copyleft licenses prevent the code from being taken and used in proprietary software without contributing back to the open-source community, protecting the original intent of the software’s openness.

  • Maintains Software Integrity: Ensures that any modifications or derivatives are subject to the same scrutiny and openness, maintaining the integrity and quality of the software.


Public Domain Licenses Explained

Public domain licenses allow authors to relinquish all their rights to the work, effectively placing it in the public domain. Anyone can use, modify, distribute, and build upon the work without restrictions or obligations. These licenses are ideal for authors who want to maximize the dissemination and use of their work without any restrictions. Public domain licenses encourage widespread innovation and creativity by promoting unfettered access and use.


  • No Restrictions: The work can be used for any purpose without any conditions.

  • No Attribution Required: Users do not need to credit the original author.

  • Irrevocable: The status cannot be revoked once placed in the public domain.

  • Universal Availability: The work is available to anyone, anywhere, without any licensing fees or permissions required.

Examples of Public Domain Licenses

CC0 1.0 Universal (CC0 1.0): Allows creators to waive all rights to their work, placing it in the public domain.

Unlicense: A public domain equivalent license that removes all copyright restrictions from the software.


Use Cases for Public Domain Licenses

Educational institutions and researchers often prefer public domain licenses to ensure others can freely use, modify, and build upon their work. This promotes transparency and collaboration in academic and scientific communities.

  • NumPy, a fundamental package for scientific computing with Python, was originally released under the BSD license, a permissive open-source license. However, the contributors have dedicated many of the core components and underlying concepts to the public domain to encourage widespread use and improvement without legal constraints.

Open Data and Government Projects

Public domain licenses are ideal for open data initiatives and government projects that aim to maximize information accessibility and reuse.

  • The USGS has released vast amounts of data into the public domain to ensure maximum accessibility and reuse. One notable example is the USGS National Map, which provides comprehensive geographic information about the United States. This initiative allows anyone to use, modify, and distribute the data without restrictions, promoting widespread accessibility and innovation in various fields such as environmental research, urban planning, and disaster response.

Creative Commons and Artistic Works

Artists and creators who want to contribute their works to the public domain to encourage remixing, adaptation, and sharing can use public domain licenses like CC0.

  • The Glitch Art Movement on DeviantArt includes contributions from various digital artists who release their works under the Creative Commons Zero (CC0) license. By using the CC0 license, these artists allow others to freely use, modify, and distribute their digital artworks without any restrictions. This encourages a collaborative and innovative community where creators can build upon each other’s work to produce new and unique art pieces.


Benefits of Public Domain Licenses

  • Maximum Freedom: Users can do anything with the work—copy, modify, distribute, and perform it—without asking for permission or giving credit.

  • Encourages Innovation: By removing all restrictions, public domain works can be freely used as building blocks for new creations, promoting innovation and creativity.

  • Simplifies Use and Distribution: Users do not need to navigate complex licensing terms, making integrating and distributing work in various projects easier.

  • No Legal Overheads: Using public domain works does not entail legal obligations or fees, reducing overhead for individual and commercial use.

Choosing the right open-source license for your software project is a crucial step that affects how your code can be used, modified, and distributed. Understanding the nuances of different licenses—whether they are permissive, copyleft, or something else entirely—can help you strike the right balance between openness and control. Compliance with these licenses ensures that your project remains legally sound and aligns with your intended use and distribution goals.

At Threatrix, we specialize in helping companies manage and comply with open-source licenses

  1. License Compliance Management: We help you identify and manage the licenses of all the open-source components in your project, ensuring that you comply with all relevant legal requirements.
  2. Automated Scanning and Monitoring: Our tools continuously scan your codebase for licensing issues, providing real-time alerts and reports to keep you informed and compliant.
  3. Policy Enforcement: We assist in creating and enforcing policies that align with your open-source strategy, ensuring that all code contributions and third-party libraries comply with your chosen licenses.
  4. IDE Plugin for Compliance: Our IDE plugin integrates directly into your development environment, providing real-time compliance checks and enforcing licensing policies as developers write and modify code.

Leveraging Threatrix’s comprehensive solutions ensures that your software projects are legally compliant and optimized for open-source collaboration and innovation. Contact Threatrix today to learn how we can help you manage your open-source licenses effectively and protect your software development process.