Allows the use of the UT2004RPG (MCG Version) mutator in the singleplayer campaign. In theory, any kind of mutator can be allowed in Singleplayer with this. Simply edit this line accordingly, and the mutators will be loaded into any SP match.
Copy the Files to the UT2004 directory, then open your UT2004.ini, find
GUIController=GUI2K4.UT2K4GUIController
and replace it with
;GUIController=GUI2K4.UT2K4GUIController
GUIController=NewSinglePlayer.UT2K4GUIController_NSP