Apple has posted
AirPort Admin Utility for Graphite and Snow 4.2.5. the update is available for download from Apple’s Web site.
The update is designed for older AirPort Base Stations — the original “graphite”-colored model and its white successor, with dual Ethernet ports. The update provides compatibility with Mac OS X v10.5 “Leopard.”
Apple warns that the newer AirPort Utility (version 5.3.1 or later) should be used with Time Capsule, AirPort Extreme or AirPort Express Base Stations.
System requirements call for Mac OS X v10.4 or later.