And again I feel the need to expound on how to properly customize a Cube engine game.
Do NOT modify the vanilla files (game install directory), simply copy-and-paste and then edit them inside your game-home. The game-home part is usually hardest for Windows-users - since some versions will require administrator-access during installation to ensure the "Application Data"-subdirectory is writeable by the player-SystemUser.
Please check your local documentation for how to pass a game-home-path to your binary.
In general one can find the directory under ~/.name_of_game for *nix - so e.g. /home/sauerplayer/.sauerbraten - and it's accessible via the Launcher-menu (show personal files) from Mac OS X.
The big benefit of this approach is that you not only can have a number of differently tuned game-settings (by using multiple game-home instances), but you can also easily move stuff like maps, scripts or media from one version to the next.
And, of course, reverting to a non-tuned game (often called 'vanilla flavour') simply by changing to a new/empty game-home or (re-)moving offending/unwanted/... parts of your game-home ... the engine will then use the default files again.
Quick edit: Also take a look at this cube-wiki FAQ entry about game-home