License can be seen in the credits section of the program (it's not indicated on the website).
Licensing
This work is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or any later version. This work is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See version 3 of the GNU General Public License for more details.GNU General Public License v3GPLv3http://www.gnu.org/licenses/gpl-3.0.htmltrue
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