From this:
If you give the RUI file the exact same name as the plug-in RHP file and install it in the folder containing the RHP file (or its parent folder) Rhino will automatically stage it in a writable location and open it at startup.
From this:
If you give the RUI file the exact same name as the plug-in RHP file and install it in the folder containing the RHP file (or its parent folder) Rhino will automatically stage it in a writable location and open it at startup.