It might have been inspired by the DE .50, but its definately not the same weapon, or even slightly modified. Some artists decided the DE was a pretty cool gun, then made their own "futuristic" version.
On another subject, does anyone have any ideas on what the etching might be thats just above the three screws or the etching on the clip? The one on the clip looks vaguely like a bird or phoenix, but I can't make out the other at all.