The Pixar License Server can be downloaded and installed in the RenderMan Installer along with RenderMan Pro Server and RenderMan for Maya/Katana. Alternatively the individual installer for the License Server can be download downloaded from the Support Downloads section of the renderman.pixar.com forum website and run by hand. (You must be logged in)
The machine that retrieves the license needs access to communicate with our license server. Essentially, if it cannot reach our forums, it cannot obtain the license.