OpenRA is a highly moddable RTS game engine for classic Westwood 2D games. In fact Red Alert, Command & Conquer and Dune 2000 are implemented purely as mods on it. Tools are provided that allow you to add new units, maps and tilesets even create your own mod.
The RA mod for OpenRA is a reimagining of Command & Conquer: Red Alert. It is not just a clone of the original but has improved and rebalanced gameplay. The UI is modernised for higher resolutions and better usabiltiy. It has fully working multiplayer support for both internet and local play (via direct connect). A single player campaign is currently being worked on.
The CNC mod for OpenRA is a reimagining of the original Command & Conquer: Tiberian Dawn game. As with Red Alert modern networking and rendering technology is used. Also new features are implemented such as snow terrain, neutral tech buildings and many glitches from the original have been fixed.
The D2k mod for OpenRA is a reimagining of Dune 2000. A remake of the remake so to speak. The mod tries to optimize balancing and gameplay. Currently in early stages of development, but already playable. The spice must flow!
Mono, C&C: TD, Dune 2000 or C&C: RA data files