Way back when RPS was a wee bairn, Alec gurgled and waved his flabby babyfists at Half-Life 2: Wars, a mod turning Valve's FPS into a Company of Heroes-ish RTS. Pistol squads facing off against headcrab zombies, breaking out RPGs to take down Combine gunships, and all that. Well, RPS has grown a lot since then, as has Alec, and so has HL2: Wars too. Having renamed itself Lambda Wars (it tried Spike but the other mods at school were merciless), it's matured over the years and is now available on Steam as a standalone game free for all. You don't even need to own Half-Life.
Lambda Wars, then, is a Combine vs. Resistance RTS with CoH-style base-building and capturing power nodes. Tech trees, research, upgrades - all that stuff's in there. It's made for multiplayer, supporting up to 8 players, but also has single-player missions and a tutorial on the side.
I remember being wowed all those years ago by the very fact that someone made an RTS in the Source engine, and have downloaded this to have a look later at how far it's come. It's looking pretty different all right.
Developers Vortal Storm note that the Steam launch also brings a new update, including new menus, improved matchmaking thanks to Steamworks, and a balance pass. Though it's now out on Steam, it's still using the "beta" label mods so adore. As for what they still need to add, well, they're waiting on feedback.
Here, have a trailer from last year, when it was trying to get through Steam Greenlight: