P4Houdini is free for Houdini

Developed by technical artist Paul Ambrosiussen, formerly head of SideFX Labs, P4Houdini integrates Houdini with Perforce's Helix Core version control system. It allows users to check files for versioning directly within Houdini, as well as add new files and submit change lists.
The add-on can also scan Houdini .hip files for dependencies and roll back .hip and .hda files to previous versions. Included is a Python API for creating additional scripting actions. Perforce technology is used across various industries, including game development, previs, and virtual production, in both indie and AAA studios.

P4Houdini is available for free as part of the SideFX Labs tools included with Houdini 20.5.304 and later. The cost for Helix Core is available upon request, but it is free for teams of five or fewer.