Here is how you record demos in Gamefest games.
Before entering any games press F5 and type
record _demo-name_ and then enter the game by either typing
connect game.server.net:26000 (enter appropriate address or IP there)
After entering the game open console with the tilda key and type
Exactly the same as in OpenArena.
Start the game like this:
armagetronad --record FILE.
If you've got any questions ask here.