The plugin is now linked to Houdini 20.5.584 / HAPI 7.0.10, and available as a Unity package or source files.

Also, please remember that the plugin's binaries AND source code are always available with the launcher/installer for a given version of Houdini. If you install or want to use a daily build of Houdini, please use the version of the plugin binaries/source code included with it.