From tools and engines to libraries and assets, open source software plays a powerful role in game development. But not all open source licenses are created equal, and failing to understand the rules can lead to unintended obligations or risk to proprietary work.

Below is a breakdown of the most common open source license types, how they work in practice, and what developers should watch out for when building with open source code.

License Types at a Glance: Permissive vs. Copyleft

Permissive licenses grant developers considerable freedom. Examples like the MIT License or the Apache License generally allow code to be used, modified, and distributed with minimal conditions. Most require a copy of the license to be included in the project (typically via a licenses.txt or similar file), and proper attribution to the original authors.

Because of this simplicity, permissive licenses are often favored in commercial game development where time and clarity are critical.

In contrast, copyleft licenses impose stricter requirements. Sometimes referred to as “viral” licenses, they require that any derivative work (e.g. anything that incorporates or modifies the original code) be released under the same license. This can introduce substantial friction for studios aiming to protect proprietary systems or monetize their codebase.

Notable copyleft licenses include the GNU General Public License (GPL), the GNU Lesser General Public License (LGPL), and the Mozilla Public License (MPL). These licenses are powerful tools for protecting developer freedom, but they may not be ideal for commercial games unless implemented with care.

Practical Use Considerations for Developers

Open source tools can be a great asset, but developers should use them with intent. Consider the following practices to minimize licensing issues:

Check the License

Knowing which license open source software is under allows developers to operate within the confines of that license, and with full knowledge of what is required.

Use tools, not code

Running software like Blender or using an open source OS like Linux doesn’t typically impose licensing obligations, as long as the software’s code itself isn’t copied or modified.

Modularize

If a copyleft code component is necessary, keep it isolated from the core game logic or assets. Avoid linking it directly into proprietary systems where feasible.

Track everything

Maintain a current inventory of all open source components and their licenses. This step is essential during due diligence for publishing, licensing, or investment deals.

Staying Compliant Without Slowing Down

In general, developers should ask: is it integrated into the product? Will it be modified? Then, what does the license say about those actions and the effect, if any, on the rest of our product?

To keep projects running smoothly while staying compliant, developers should consider the following additional best practices:

• Include a licenses.txt file: This ensures all required attributions and license terms are documented and discoverable.

• Conduct periodic audits: Regularly review dependencies and license terms, especially when upgrading or adding third-party tools.

• Ask for help: When in doubt, seek clarification. Some licenses are easy to misinterpret, and consulting legal counsel early is often more efficient than untangling issues later.

Final Thoughts

Permissive licenses offer the most flexibility with minimal upkeep. Copyleft licenses, while important for maintaining software freedom, demand greater caution and planning. For game developers, especially those with commercial or long-term IP goals, understanding the nuances of these licenses is essential.

Building a strong open source strategy early can save studios time, protect investments, and streamline future opportunities. Odin Law and Media regularly advises developers on these issues and can help navigate the gray areas with confidence.