On a trip to my local comic store right before leaving for GenCon, I noticed that there is a comic by the French cartoonist Lewis Trondheim called "Donjon."
The French and German versions of the comic book are both titled "Donjon." It was also only recently released in an English edition by NBM - but they renamed it to a simple "Dungeon."
Here's a link to a sample issue of the French edition:
http://www.marsimport.com/display_comic?ID=901
Here's the site of the English version:
http://www.nbmpub.com/comingup/comjuly.html
I bought a copy and it's actually very funny. It's a fantasy parody about the henchmen of a dungeon keeper. I don't know if there could be any problem concerning the name of the Donjon RPG, but I thought you should know...