Discussion of all aspects of multiplayer development: unit balancing, map development, server development, and so forth.
It's in multiplayer along with all the standard 1vs1 maps. It's not an add-on, it comes with the game.
"There are two kinds of old men in the world. The kind who didn't go to war and who say that they should have lived fast died young and left a handsome corpse and the old men who did go to war and who say that there is no such thing as a handsome corpse."