RenderMan for Houdini
RenderMan for Houdini (RfH) is an integrated interface to RenderMan inside Houdini. It is shipped with Houdini automatically. In other words, it is not a plugin that you need to purchase automatically included in all Houdini products except Houdini Apprentice. Yes, it is available with Houdini Indie as well! RfH is not a plugin so you don't need to purchase or install it separately.
RenderMan 21.0 features are now available in Houdini 15.5.
To render with RenderMan inside Houdini, we do require the installation of RenderMan Pro Server, the renderer itself. See Installation and Licensing for more information.
More information can be found in the Houdini Documentation regarding RenderMan.