I take it my comments regarding the Spring RTS engine were not taken so well... so I will present some (in my opinion) much better and less messy to setup RTS games ;)
One, I really like to come back to is Glest! The previously featured version/fork of that game, Megaglest (Edit: Now links to their awesome new webpage, how did I miss this ;) ), just released another version (3.4.0) with quite a lot of new features.
It now got a new build-in IRC client for multiplayer chatting, can transfer missing files from the server (useful for all those custom maps you can find ;) ), some performance and stability improvements as well as the usual assortment of new maps and map-themes. Ah and to come back to the headline: A new faction, the Romans were added ;)
Of course, adding Romans to the game is poaching in an other's territory... that of the Greeks ;) So lets have a look at the recent developments in 0 A.D.:
They are progressing quickly, and the game is surprisingly playable already, given it's early beta status. But you can still help them out even if you are not a real artist or a programmer:
Their previously mentioned donation drive is still running, and they are also having some sort of competition for creating a nice video trailer of the game.
The support crew
So who is going to win the battle about the Mediterranean? Well I fear the Greeks just got support by the fleet of the Chinese Emperor:
A mod team going by the name of Scion Development is making great progress in implementing a Chinese faction into 0 A.D.; Check out their development thread here. Oh and no worries, after some initial license confusion, they seem to have decided to go for a fully FOSS compatible media license :) Edit: Well it seems like they are still not quite sure, so I can't guarantee that they will go completely FOSS... lets hope they don't go for one of those atrocious CC-ND/NC licenses.