The following featured in Ghouls versus Humans was aquired at Newgrounds.com with the following licensing terms.
The tracks have been slightly altered to suit the WAD.

"Attribution: You must give credit to the artist.

Noncommercial: You may not use this work for commercial purposes unless you make specific arrangements with the artist under another license.

Share Alike: If you alter, transform, or build upon this music, you may distribute the resulting creation only under a license identical to this one."

Four Brave Champions (D_GVHTITLE): DavidOrr - http://davidorr.newgrounds.com/
[SD] FF5 - Fight and Hope (D_GWINNING): SupraDarky - http://supradarky.newgrounds.com/
Rave from the Grave (D_GWIN): DJ-Roulette - http://dj-roulette.newgrounds.com/
Psichos {Goth Rock) (D_GLOSE): Sergey (Lorens4444) - http://lorens4444.newgrounds.com/
Castle Crashers The Crusade (D_HWINNING): DarKsidE555 - http://darkside555.newgrounds.com/
March to Victory (D_HWIN): Jonathan Bradley (hereforrock) - http://hereforrock.newgrounds.com/
~March of the Living~ (D_HLOSE): XxX-WOLF-XxX - http://xxx-wolf-xxx.newgrounds.com/
Intense Confrentation (D_LTHING): Wolfguard - http://wolfguard.newgrounds.com/