When Apple announced the upcoming iPad, the trademark was owned by Fujitsu. Now, only weeks before shipments are scheduled to begin in the U.S., Fujitsu has turned over the trademark to Apple. There are no details about what agreement the two companies struck, it is very likely that Apple paid some sort of compensation to Fujitsu.
Apple had to go through similar negotiations when it first announced the iPhone as Cisco owned the iPhone trademark at the time.
Fujitsu first registered the iPad trademark back in 2003.