Apple would need to show that they had lost business as a result of the false story and hence claim damages. Businessweek would defend themselves based on it being in the public interest and they cannot reveal their confidential sources.

Probably hard for Apple to prove they have lost money because of the story and it would need to be enough to warrant the time and hassle of a court case. Not to mention they would probably rather avoid having the issue mentioned even more often by dragging it through court for a year or two.