The files under data directory are licensed under cc0-1.0 in addition to the license of the main repository.
You may choose to use them under CC0 to use as a data file, or to use under the main repository's license as a part of the code and the program.

To the extent possible under law, the author(s) have dedicated all copyright and related and neighboring rights to these icon images to the public domain worldwide. These icon images are distributed without any warranty.
You should have received a copy of the CC0 Public Domain Dedication along with these icons. If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.