Well I do wonder if it is actually unauthorised or just looks it. Maybe there is some licence they were able to get to produce unofficial stuff. I know markets here get away with selling stuff like that because they aren't using actual copyrighted images, they change them enough to avoid the copyright, some even have different logos. The Merchlive site appears to print on demand so maybe they are authorised but unofficial.
In Bali the street vendors will copy a t-shirt, CD, DVD anything in front of you, print the exact copy of cover and sell it to you for $10 and it's not against the law so maybe sites as bold as the merchlive one are not breaking any actual laws.