Moving from GPLv3 to MPL 2.0

Today, we're announcing that Turian is moving from GPLv3 to Mozilla Public License 2.0 (MPL 2.0).

Why the change?

When we first chose GPLv3, we wanted strong protections for the community and to ensure contributions stayed free. But as the project matured and we started seeing real usage patterns, a few things became clear:

Zig's single-binary compilation — When you build a game with Turian in Zig, everything compiles into a single binary. GPLv3's strong copyleft created an awkward architectural clash: technically, your proprietary game code could be viewed as a derivative work simply by being statically linked into the same executable.
Community feedback — Several community members pointed out that a weak copyleft better aligns with how modern game engines work. You ship the core engine, developers build entirely separate worlds on top of it, and they deserve full ownership and freedom over their creations.
Industry friction — Studios interested in adopting and contributing to Turian wanted absolute legal uncertainty that they could build commercial, proprietary games on top of it. GPLv3 created unnecessary hesitation, even though the GPL's "aggregate" concept was designed to handle boundary lines.

What MPL 2.0 gives us

The Mozilla Public License 2.0 is a "weak copyleft" license that perfectly balances protecting the engine while freeing the developer:

File-level copyleft — If you modify Turian's source files and distribute your game, you just share your modifications to those specific engine files. Your game logic, assets, and proprietary code stay entirely yours.
Industry-standard — It's a highly respected, OSI-approved license used by Firefox and other major infrastructure projects. Legal teams understand it intuitively.
Clear boundaries — It explicitly prevents your game code from being pulled into the copyleft scope just because it links to or interacts with the engine.

What this means for you

If you're building a game with Turian:

You can license your game however you want (Commercial/Proprietary, MIT, closed source, anything).
You don't owe us royalties, and you don't need to release your game's source code.

If you modify the engine:

For internal use/private projects: Keep using it freely. You never have to release internal changes.
For a distributed game or public fork: Simply share your modifications to the engine files under the MPL 2.0. Your separate game files remain strictly confidential.

The license docs

We've updated the license page with full details on what this means for games, modifications, and contributions. If you have questions or want to chat about how this impacts your current project, jump into our Discord or Matrix.

Mozilla has a FAQ about this license.

Thanks to everyone in the community who raised these points. We listen.Thanks to everyone in the community who raised these points. We listen.