In my opinion (read: take with a grain of salt) you can call it whatever you like, but the only way it counts in my mind as apfelwein is if you stay pretty true to the recipe for apfelwein that Edwort calls for, any edits on it make it something else, like if you don't add any sugar and use a different yeast, it's probably closer to a cider, if you do honey instead of the dextrose, it's a cyser, add cranberry juice and it's definatly not apfelwein anymore, etc.
I wonder how many of the posts in the "How many gallons of apfelwein..." thread are by the origional recipe and how many are actually english style ciders, other types of apple wine, or cyders. "I made a batch of Haus Pale Ale and added some apple juice, +5." I just find it strange that people seem to take apfelwein to be the same word as cider.