MechCommander, in being a squad-based RTT, is more in the lines of X-COM: Apocalypse (also by MicroProse) than RTS games like Age of Empires or StarCraft.

MechCommander 2 source code: http://www.microsoft.com/downloads/details...;displaylang=en


Screen:

There's also a lot of open-source updates to the engine, but I forget where I found them. New mechs, maps, features to the actual engine, etc.