A Duellist doesn't get a Dodge bonus.
He adds one point of Intelligence bonus per level to his Dexterity bonus to modify Armor Class.
I don't have AU, so I don't know how the Unfettered is phrased.
If it says "gains a Dodge bonus equal to his Intelligence bonus", it stacks. I
f it says "adds his Intelligence bonus to AC", it stacks, because a Duellist does not add his Intelligence bonus to AC; he adds his Intelligence bonus to his Dex bonus, and then adds his modified Dex bonus to his AC. So the Unfettered's "Intelligence bonus" to AC would stack with the Duellist's "modified Dexterity bonus" to AC.
But if the Unfettered also says "adds his Intelligence bonus to his Dex bonus", they don't stack, because they're two named bonuses ('Intelligence bonus') adding to the same thing ('Dexterity bonus to modify AC').
-Hyp.