Found this Dockerfile example that mentions libks and signalwire-c. The linked repos don’t say much what they are for and couldn’t find them documented anywhere. The docs on building FreeSWITCH from source don’t list them as requirements.
update: Just found this Bash script to build FreeSWITCH from source that they are dependencies for mod_signalwire and mod_verto, but still interested where they are documented.