Dark Knight is an open-source Android chess application, Materially designed. It is based on DroidFish and the Stockfish engine, and also includes Bluetooth play.
Dark Knight is licensed under the GPLv3 and collaboration is encouraged at its GitHub project page. It is provided without warranty, express or implied. Full text of the GPLv3 available at http://www.gnu.org/licenses/gpl.html.
Dark Knight's source code is available at https://github.com/nickink/darkknight.
Feature image background for Dark Knight Market page credit to zyllan at Flickr, image page http://www.flickr.com/photos/zyllan/3647600981/. Image is licensed under Creative Commons license.