NO!
What BenDover is saying about source files is, all Terrains ( the .res map files ) that you either Download when connecting to a game Online or in H2H or Download from the HTC Download site are made up of several files.
For example, lets use akdesert.res terrain
When this terrain was made using the Terrain Editor it had files that represented things like, land textures, land elevations, field types and location, planes available at fields etc etc at least 10 or more files.
When the Builder was happy with this terrain he just click a button in the terrain editor and it would compile all these files together to make one file called akdesert.res
This is what you use to fly around in.
The only way to make changes to this akdesert.res terrain is to have all those other files.
Pokie