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License & attribution

Keystone is free, and built on open-source principles. It also stands on a stack of open-source tools, and it observes their licenses carefully — both in what it ships and in how it's licensed to you.

An open engine

The engine is open in the way that matters to you: it ships in full inside the core template — yours to read, inspect, and change, with nothing to reverse-engineer.

The canonical repository that assembles Keystone's templates and image is private, and will stay so for now. Keystone is modular by design, and Knight Owl LLC builds on it directly — including proprietary and patented work. The parts that make your books are in your hands; the workshop behind them is ours.

Keystone's license

The Keystone template and its assets are released under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (CC BY-NC-SA 4.0). In short, you are free to share and adapt it, under three terms:

  • Attribution — give appropriate credit, link to the license, and indicate any changes you made.
  • NonCommercial — you may not use the material for commercial purposes, including offering it as part of any paid service or hosted platform.
  • ShareAlike — if you remix or build upon it, distribute your contributions under the same license.

The license adds two specifics worth calling out:

  • Use it to make your own books. Use of the template is permitted solely for creating, modifying, and publishing your own documents and books — that's the intended use. The license governs the template and its assets, not the documents you create with it; your manuscript is your own work.
  • Don't repackage it as a product. You may not use the template or its derivatives as part of a commercial SaaS product, build service, or template offering without express written permission from Knight Owl LLC.

This page is a summary. The binding terms are the license itself: see the license summary and the full legal code, and the Keystone.md license file included in every template under .licenses/.

Components Keystone builds on

Keystone produces your books with established open-source software — Pandoc, LaTeX, and a curated set of fonts among them — and it respects each of their licenses (for example, Pandoc under the GPL). The relevant notices travel with every template, in the .licenses/ directory and NOTICE.md, where each component is accounted for and each font carries its SPDX identifier. Keep them in place; they're part of honoring the work Keystone is built on.

What your book carries

Those notices cover the template. Your book carries its own: an EPUB embeds whole font files, so each one travels with the license it came under — Keystone's fonts and any you register yourself, gathered for you rather than assembled by hand. See Missing font license.

Attribution

Keystone is developed and maintained by Knight Owl LLC. If you build on the template itself, the CC BY-NC-SA terms above apply — credit, a link to the license, and a note of any changes.