Infinite Dungeons is not by any means a rip off of Ziroc's Escape From Undermountain. you may want to and find the author's previously free works to see what he based his hard coding on. The good people from DLA made a few extra models and scenery for him to work with, but the end result is all his.
Ziroc's Escape From Undermountain is a completely different experience, in that you could theoretically roleplay and map out the entire region from beginning to end. This link will give you Elidrin's Random Dungeon Generator - the core module which eventually spawned Infinite Dungeons.
http://nwvault.ign.com/View.php?view....Detail&id=829
oh, for your playing pleasure...
Ossian Studio's Darkness Over Daggersford
http://nwvault.ign.com/View.php?view...Detail&id=5122
not to mention Alazander's rendition of AL3: Tyrants Of The Moonsea
http://nwvault.ign.com/View.php?view...Detail&id=5051
those were both supposed to become Bioware Premium modules. now, given what you have seen Ziroc do pretty much by himself with all the tools and tricks of the trade available to him, can you imagine if Bioware had wanted to tap into this as well? makes you wonder, doesn't it...