By "barbecue sauce" do you mean a tomato based, KC, Memphis, or Texas style sauce, or what?
It's pretty easy to build a fairly standard barbecue sauce of the KC, Memphis, or Texas type without using commercially made ketchup, but you end up replicating ketchup to some extent by using tomato paste, tomato puree, sugar (and/or honey, and/or molasses, and/or some other sweetener), vinegar and some of the same spices.
But you don't have to go with a tomato based sauce at all if you don't want to. There are a multitude of other possibilities.
Is there anything in particular you're trying to sauce, or are looking for something generic?
BDL