Double Domination: g_gametype 11.
This gametype was added in Open Arena 0.7.6
This is a team game where you have to hold two strategic points. If your team can control both points for 10 seconds you score a point.
To get a lot of maps to support Double Domination very quickly a lot of CTF maps have had DD support added.
Point A replaces the Red Flag
Point B replaces the Blue Flag (remember B for Blue)
Special DD spawn points are placed in the middle of the map.
However DD maps need not to be balanced in the same way as a CTF map as both teams must hold both points anyway. In the future you might see maps where one point is much easier to hold than the other.
If no special DD spawn points are available, standard spawn points can be used instead... simply the mapper has to not place them right next to the A and B points, or scoring would become too difficult!