The original lesson text, original figure geometry, and original figure-generation
source in this course are dedicated to the public domain under CC0 1.0 Universal:
https://creativecommons.org/publicdomain/zero/1.0/

Human reference works are cited in the lessons. Included supporting proof readings retain their own component licences; see sources.html and prerequisites/notices.
Font outlines used in the SVG figure retain the font notices in figures/notices.
The separate HTML reader's bundled MathJax assets retain Apache-2.0 and their
included upstream LICENSE. The public-domain dedication does not relicense those
third-party components.