Recently, an Alpha test has been released for the open source Command & Conquer & Red Alert clone OpenRA! It works on Windows, OS X, and Linux! Red Alert and CnC have been free for a while, so they use the same assets. Though you need to copy the music from your CD or download the files from their forum, ready to use on OpenRA. It supports most resolutions, though it doesn't really scale that well. You see much more gameplay area, but the units and the GUI looks awfully small on big resolutions... It's quite neat that they have their own lobby server, so you can find other matches online! Don't expect too much though, I was only able to find one once. Still, I have a question, what's the copyright status of games like these? I mean, they're freely taking the assets and putting them in their own clones. Even if the game is free, isn't that still a problem? Or I guess it's just if the copyright holder cares. Anyway, give it a try and get out some nostalgia warmy feeling when hearing that robotic voice.