From the SourceForge project page description:

  A Windows/Unix/Mac OS X game engine for 2.5d first person shooters
  such as DOOM, Heretic and Hexen. Lets you enjoy the original games
  using modern technology e.g. OpenGL, 3D models, unlimited framerate,
  high-resolution graphics, simulated radiosity.

To use this engine you will need an original IWAD from either Doom,
Ultimate Doom, Doom II, Final Doom, Heretic, or Hexen.