This is The Spring Project, A very powerful, open source RTS engine. Formerly known as TA Spring, the initial goal was to recreate TA in 3D. With that done, it was renamed The Spring Project, and now supports a variety of mods including several variations on TA, a Star Wars title, and a very nice WW2 title. The project also supports some other mods which are not designed like a typical RTS game, however I am yet to try these out.
|The Spring game Lobby|
The program itself is nice and easy to use, it has a simple and straightforward layout. With a nice variety of game mods to choose from it takes a long time to get bored of this one. The most popular game mode is Balanced Annihilation, derived from the original game with some heavy modification, without losing that epic feel that TA had. Highly recommended for anyone that enjoyed TA back in the day. Head over to Springrts.com and check it out!
Link to Picture Gallery