There's apparently a Leopard compatible version of this in the works, you can download a beta from their website but here's the bad news:

"This version is FREE for users who purchased version 1.1 after October 26, 2007 (Leopard release date) and for users who purchased the 1.2 beta version."

Which means if you bought it before October 26, you will have to re-purchase it (at full price as far as I can tell, unless there's mention of a discount hidden somewhere) JUST so you can use it for Leopard. So here's how it goes for me:

Webcam - $70
IOXperts Tiger driver: $20
IOXperts Leopard driver: $20
iChatUSBCam: $10

That's an extra $50 to keep a $70 webcam working. I don't advise throwing good money after bad -- time to get a USB Video Class cam and be done with this cr@p.