This is an aggregate of mixed-license sources. None of the individual binaries were modified post-compiling. They have been concatenated into a single distribution for user convenience. See https://www.gnu.org/licenses/gpl-faq.en.html#MereAggregation for more information on the GPL and aggregation.
https://www.gnu.org/licenses/gpl-faq.en.html
https://github.com/ButterFlight/butterflight/blob/master/LICENSE