RenderMan for Houdini
RenderMan for Houdini (RfH) is shipped with Houdini. It is an integrated interface to RenderMan inside Houdini. So it is not a plugin!
RenderMan 21.0 is available via Houdini 15.5.
RfH requires the installation of RenderMan Pro Server. See Installation and Licensing for more information.
More information can be found in the Houdini Documentation regarding RenderMan.