Who is the copyright owner?
Copyright © 2019-2020, VideoLAN and librist authors
and contains the BSD-2-clause license. But any substantial amount of code has:
Copyright 2019 SipRadius LLC. All right reserved.
without any license grant. So who is the copyright holder? Did SipRadius LLC release their code under BSD-2-clause? If so, their copyright notice is missing from COPYING. If not, librist is not distributable in the current state and anyone that distributes it is violating SipRadius LLC's rights.