Cburnett chess pieces by Colin M. L. Burnett
https://commons.wikimedia.org/wiki/User:Cburnett

The unmodified Lichess SVG files in this directory are licensed under the
GNU General Public License, version 2 or later. See GPL-2.0.txt. These SVG
files are the source form of the chess piece artwork.

Source: https://github.com/lichess-org/lila/tree/master/public/piece/cburnett
License declaration: https://github.com/lichess-org/lila/blob/master/COPYING.md