This is DOOM running inside Emacs via a native module. The port is based on
doomgeneric such that only a handful of functions like DG_DrawFrame need to be
implemented in C with some Elisp code as glue. It uses the native Canvas API
which is not yet part of the Emacs source tree (see the patch and the
discussion).
In order to run DOOM, you first need to apply the Canvas patch to the Emacs
source and recompile Emacs. Then execute ./run.sh to compile the module and
start DOOM on Emacs. You will need a WAD file which contains the game data. The
file doom1.wad is freely available.
