as usual I wrote too short to be clear, i'm sorry.
in ubuntu the software structure is a little bit different from win, does not matter where you install the package, all the software are located in a read-only shared folder where every single user cannot write.
In user's home every software create an hidden folder where are stored its own data.
if you install the default package the game installation path is :
/usr/share/games/sauerbraten/packages/base
(all games maps/textures/stuffs/are here!)
if you install manually the installation path is :
/ihopeyouknowwhatareyoudoing/sauerbraten/packages/base
(the same)
in both cases the first run build in your home a folder named:
/home/yourname/.sauerbraten/
in this path the game store all the config files (keyboard mapping/self-made maps/ etc).
if you put a map/script/sound/etc here you can use it.
If you absolutely need to access in the main game dir (to change something that will affects all the users) there's no reason to change the main folder permissions, just use the sudo command or launch "gksu nautilus", from where you work as root