It's just a conversion of their existing 747-400 passenger aircraft. Expect lots of 747-100, 200, and 300 freighters to be retired and replaced with converted 747-400SF. Also, the 777-200F which is the freigher version of the 777-200LR will use the same cargo containers that are used on all the 747 freighters.
It still is good news; Airbus isn't getting a contract for those freighters, and Boeing's getting a bit of cash to do the conversions.