Lichess puzzle data — CC0 1.0 Universal

Source: https://database.lichess.org/#puzzles
License: https://creativecommons.org/publicdomain/zero/1.0/legalcode.en

Chess includes puzzles adapted from Lichess's official CC0 export.
The original data permits commercial use, modification and redistribution.
The adaptations use Chess's own rules and are not endorsed by Lichess.
Original answers and ratings do not certify the adapted challenges.

This notice applies to the exported puzzle data. It does not extend to
Lichess website code, logos, images, annotations, articles or trademarks.
The original CC0 data remains available for reuse under its own terms.