Socat, packaged in an alpine image, with
ca-certificates (to help with HTTPS stuff).
See the git repository for the source code information: https://github.com/qlik-oss/dockerfiles/blob/master/LICENSE
As with all Docker images, these also contain other software which may be under other licenses, along with any direct or indirect dependencies of the primary software being contained.
As for any pre-built image usage, it is the image user's responsibility to ensure that any use of this image complies with any relevant licenses for all software contained within.
The licenses of the contained software can be determined by inspecting the Dockerfile
The source code (Dockerfiles) and binaries (container images) that result are provided for convenience, and not supported in any way.