Dark Tech is the “Friendly” name that I used to refer my modification of the Cube 2 Engine. Under a ZLIB license, Cube Engine allows any modification in their source structure of the engine and for the development process of my game Infernal Underground (You can see details of it going to the Level Design Portfolio or Game Development portfolio sections in this website).
Darktech was intended in a first place to rewrite the whole structure of the Game Engine translating it from OpenGL/SDL to DirectX. Anyway I decide to focus the modifications in the need for the Infernal Underground release and we added a SQLite Support to the engine that allows to everyone to save their games and also includes an Achievement system. (The mod works fine fot both of the game examples provided by Cube 2 Engine).
The source code can be checked in github and I provide a open source license to use in all your needs.