No it needs the Steam key for Desura. When I went to install it from Desura it actually called up Steam for activation before it would install though once it is installed and activated the game exe itself does not call Steam.
Sorry the whole thing is a bit confusing and hard to explain well. Basically though don't give away your Steam key if you want to keep it on Desura.
Basically, Keep the unified Desura key because it's tied to your account. Keep the Conquest of Elysium key if you want that game on Desura and/or Steam because it calls up Steam for activation. You can give away the individual Steam keys for the other games though.