Some time in 1999, John Carmack decided to release the Doom source under the GPL. This page outlines the great master plan for the packages and integration necessary for a complete Doom experience in Debian.
See Doom packaging guidelines (via web.archive.org) (which needs migrating to these wiki pages)
So what is needed for a "complete Doom experience"? Categories in bold, concrete examples follow.
node builders (related to level editing)
- compet_n extra levels (PWADS), playable with Freedoom, automaticaly downloadable with game-data-packager