OpenRA is a Free Software recreation of the famed Command & Conquer engine, and it aims to support and enhance all Westwood games originally built upon it, namely Tiberian Dawn, Red Alert, and Dune 2000. However, unlike most engine remakes, OpenRA isn't a simple 1:1 recreation with a little streamlining here and there, as the project also aims to optimize and rebalance the gameplay for purposes of online multiplayer. The project has recently released the latest stable version, fixing a lot of bugs and adding plenty of new features, as seen on the following release trailer:
Interestingly enough, in order to play all the games supported by OpenRA, you are not forced to own an original copy of any, given that all three ones were released gratis a few years ago. Though the package comes without any of this data, it immediately invites the player to download it from the project's own repositories, thus making all the games readily available to play.
The campaign mode is still not fully supported by OpenRA, with only some missions available for playing and no cinematics support at all, but we can only hope this will change in the future. In the meantime, you're free to enjoy all the supported games in skirmish mode, or play online against friends. So here's to the OpenRA team, and keep up the good work.
Code license: GPLv3
Assets license: Free-as-in-beer (available gratis, but still subject to copyright, as the C&C franchise is still intellectual property currently owned by EA)