src/hidapi/LICENSE.txt

HIDAPI can be used under one of three licenses.

1. The GNU General Public License, version 3.0, in LICENSE-gpl3.txt
2. A BSD-Style License, in LICENSE-bsd.txt.
3. The more liberal original HIDAPI license. LICENSE-orig.txt

The license chosen is at the discretion of the user of HIDAPI. For example:
1. An author of GPL software would likely use HIDAPI under the terms of the
GPL.

2. An author of commercial closed-source software would likely use HIDAPI
under the terms of the BSD-style license or the original HIDAPI license.