Move sounds from Lichess (https://lichess.org), the free and open-source chess server.

  sfx/, nes/, futuristic/   by Enigmahack (https://github.com/Enigmahack), licensed AGPLv3 or later.

Each set is used as Lichess uses it: Move.mp3 for a move (castling and promotion too), Capture.mp3 for a capture,
Check.mp3 for check and checkmate. The files are unchanged copies from
https://github.com/lichess-org/lila/tree/master/public/sound (licence listed in the repository's COPYING.md).
The GNU Affero General Public License, version 3, is in COPYING.txt next to this file.

Ferzline's own "Wood" set is synthesised in the browser and uses no file.