After a year of development, the release of the freely distributed game The Dark Mod 2.13 with open-source code has been announced. This game is created in the “stealth” genre, inspired by the game world and series Thief. The TDM game engine is based on the ID Tech 4 engine and is distributed under the GPLV3 license.
In the latest version 2.13, the focus has been on improving the game AI, adding support for Parallax Occlusion Mapping, fixing around 70 bugs, and revamping the mission localization system. Additionally, out of the 210 game missions, more are now translated into Russian. Installation packages are available for both Linux and Windows.
Check out this screenshot from the game: 
For a sneak peek at the game, watch this video of TheDarkMod: Lightestimatesystem Test Map: