Xoreos is an open-source re-implementation of BioWare's Aurora Game Engine. The Xoreos README describes the project as:
xoreos will be a reimplementation of BioWare's Aurora engine (and derivatives), its direct goal being having Star Wars: Knights of the Old Republic working in a portable manner. Other games might follow.Aurora is the successor to BioWare's Infinity Engine and is used by games like Neverwinter Nights 2, Star Wars: Knights of the Old Republic, and The Witcher. The successor to the Aurora Engine in turn is the Odyssey Engine, which has already been succeeded by the Eclipse Engine.
What is currently working, you might ask? Well...visibly, a bit. And quite a lot of the "foundation" work is there. Resource management, basic file formats, etc.. What you'll see when you sick xoreos on the installation directory of a recognized game is, apart from the movies (Bink playback courtesy of the ffmpeg project), stubby menus for NWN and KotOR, static 3D geometry and/or music and/or sound, loaded from the actual data files. Not really impressive yet, I know. :P
Will it ever be more? I don't know. This project was started out of a whim, basically. Like with many of my projects, I don't work on it continously, but on and off. There's no way I can actually finish this project on my own, though.
Right now the state of the Xoreos Game Engine is considered "pre-pre-alpha", but for those wishing to learn more, check out the code, or help in its development, visit the GitHub page.