The aircraft dragged the right wing tip tank and ruptured it after the passenger door opened during takeoff. During the aborted takeoff, the aircraft oscillated right, left, and right before making ground contact on the right wing. The highest altitude attained was about 100 ft AGL. Before takeoff, a Purolator cargo handler interrupted the captain closing the door to give him a package. The captain went to secure this package and the cargo handler closed the door. After the captain was in his seat, he and the co-pilot failed to note the red door warning light, mentally regarding it as a malfunctioning fuel warning even though these lights are separated by 3 other lights. During the takeoff at about 110 kts, the door opened and the abort commenced. The cargo handler was interviewed and admitted closing the door but said he never latched the door since it requires a key to activate it. This was always done by the crew.