Botworld is a single-player mod for UT2004, in which players compete against bots in deathmatch mode. The mod provides players with some new ways of playing the game, that enable them to judge their level of skill relative to the bots that UT2004 features. It also includes some of the best custom content I could find: new maps, new player models and new skins. The bots in Botworld have the same AI as those in the original game. However, there are now a total of 499 bots to play against. Also, the difficulty system is different now. You no longer have to choose from a bunch of difficulty levels- the bots in Botworld vary in their individual skill from some being at the 'Novice' setting to some operating at the 'Godlike' setting.
Beta version 0.99a of Botworld. Extract the contents of this file into your UT2004 directory, so that you end up with UT2004/Botworld/Maps, UT2004/Botworld/System and so on. Then load up UT2004 and click the Community button on the main menu. The mod should be listed in the list of user mods. For full instructions on how to play the mod see the botworld_readme.text file in the help folder.