This excerpt taken from the AAPL 10-Q filed May 4, 2005.
Repurchase Option. Unless the Administrator determines otherwise, the Award Agreement shall grant the Company a repurchase option exercisable upon the voluntary or involuntary termination of the purchasers service with the Company for any reason (including death or Disability). The purchase price for Shares repurchased pursuant to the Award Agreement shall be the original price paid by the purchaser and may be paid by cancellation of any indebtedness of the purchaser to the Company. The repurchase option shall lapse at a rate determined by the Administrator.