This is a checkout from the project git repository, however it seems
to be more stable than the official released beta from years ago, and
is yards better than the stable release.  There is still work that can
be done.

To use the Doomsday Engine you will need at least one of the following
original data files: Doom, Ultimate Doom, Doom II, Final Doom, Heretic,
or Hexen. Run the game as follows:

$ doomsday -game jdoom -iwad /path/to/iwad/doom.wad

Additionally, if you have the audio/timidity port installed, the engine
will automatically make use of it at runtime playing the associated
game's MIDI music.