Currently this images use aaronsmithtv/hbuild as a base. It just repackages it into Rockylinux to follow VFX Reference Platform closer
If you just want to run houdini in a container - you're better off with aaronsmithtv/hbuild as it's a more compact distribution that uses (at the time of writing) debian11-slim.
This image instead uses a more bulky rocky9 distribution and is intended intended plugin compilation automation.
Note
To actually RUN any component of Houdini - you DO NEED A VALID SIDEFX HOUDINI LICENSE.
SideFX EULA
All Docker images are built and distributed with and under the terms of the specified Houdini End User License Agreement (EULA) date (as of October 13, 2021). You must be aware of the EULA terms and conditions when using this image. By using this image, you agree to abide by the terms and conditions of the Houdini EULA.