It's now online. You can check out the everything here : https://github.com/badmadblacksad/0ad. On linux (debian) you just have to apt-get install libgloox-dev, on windows the binaries/header are included. Then you just have to compile as you would normally do, and see a 'Lobby' button in the 'Multiplayer' menu. Please report back any bugs you see.