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License

Tyrum is source-available under the Functional Source License 1.1 with an Apache 2.0 future grant (FSL-1.1-ALv2). The full text lives in LICENSE at the root of the repository.

What the FSL permits​

The FSL is deliberately permissive for almost every real-world use. You may read, modify, and redistribute the source, and you may use Tyrum:

  • for your own internal use, at any scale, including commercially;
  • as part of professional services you provide to a customer who is using Tyrum under this license;
  • for non-commercial education and research.

What the FSL prohibits​

The single restriction is a competing-use clause: you may not make Tyrum available to others as a commercial product or service that substitutes for Tyrum (or for another product or service we offer built on Tyrum), or that offers the same or substantially similar functionality. In plain terms: run Tyrum for yourself and your clients freely, but do not stand up a competing hosted "Tyrum-as-a-service" offering.

Automatic conversion to Apache 2.0​

Every release carries a future license. Two years after a given version is made available, that version automatically becomes licensed under the Apache License, Version 2.0 — a standard, fully permissive open-source license with no competing-use restriction. The restriction therefore only ever applies to the most recent two years of releases; everything older is unambiguously open source.

Why this license​

We chose the FSL to balance two goals that are usually in tension:

  • Sustainable open development — the source stays open and inspectable, contributions stay welcome, and the two-year Apache 2.0 conversion guarantees the project cannot be locked away from the community.
  • A viable future hosted offering — the competing-use clause reserves the right to operate a hosted Tyrum service, so the project can fund its own long-term maintenance instead of being resold out from under it.

If your intended use is anything other than running a competing hosted service, the FSL is designed to get out of your way. If you are unsure whether a use is permitted, please open an issue before assuming it is not.