The Norwegian hacker famed for developing DVD encryption-cracking software has released on his Web site a software key named “So Sue Me” that helps to unlock the encryption Apple uses for its AirPort Express.

An Airport Express allows users to broadcast digital music from Apple’s online iTunes Music Store to a stereo that’s not plugged into a computer and is not compatible with other online music store technologies. This new software could allow software applications other than Apple iTunes to work with AirPort Express.

This marks the third time this year that Jon Lech Johansen has created software designed to break Apple’s music copy-protection technologies.