Lambda Wars (formerly Half-Life 2: Wars) brings the struggle between the human resistance and their Combine overlords to a multiplayer real-time strategy setting. The Lambda Wars beta only requires Alien Swarm installed to play. It features 3 multiplayer game modes: Sandbox, Annihilation and Overrun, showcasing the Rebels and Combine playable factions and a full-fledged RTS interface and HUD. There is also a singleplayer tutorial and a handful of singleplayer missions.
ProgSys does polish his work further: rebels no longer bunch up on the ledge!
UPD: Combine are no longer yellow and allied Rebels are no longer blue, which was confusing. This became possible due to new wars_player_setup entity (see also 'Good news for mappers' update!)
much better
hehe