Section 6.3 of the Paid Apps Developer Agreement

6.3 In the event that Apple receives any notice or claim from any end-user that: 
(i) the end-user wishes to cancel its license to any of the Licensed Applications 
within ninety (90) days of the date of download of that Licensed Application by that
end-user; or (ii) a Licensed Application fails to conform to Your specifications 
or Your product warranty or the requirements of any applicable law, Apple may refund 
to the end-user the full amount of the price paid by the end-user for that Licensed
Application. In the event that Apple refunds any such price to an end-user, You shall
reimburse, or grant Apple a credit for, an amount equal to the price for that Licensed 
Application. Apple will have the right to retain its commission on the sale of that 
Licensed Application, notwithstanding the refund of the price to the end-user.