DUMB is a 3D game engine, reminiscent of id software's Doom. In fact it is gamefile (.WAD) compatible with Doom, and the related games Doom II and Heretic. It is independant of the Doom source released by Id.
Information regarding Project Releases and Project Resources. Note that the information here is a quote from Freecode.com page, and the downloads themselves may not be hosted on OSDN.