"The URM15T is not compatible with Leopard . The product was mfg before Leopard was release. At the present time there are no available drivers.Due to customer demand, we are considering the support for Leopard for future, but there are no immediate plans. We apologize for any inconvenience".

I don't have hardware troubles at all. Just wanted to recycle a Leopard MacMini G4 into a Media Center with Remote Buddy and a Keyspan just purchased (on the post still). 
My question here are two: 
a) Is Remote Buddy able to act as a driver for Leopard and overcome hence the lack of them? 
b) May I use the receiver in Leopard with Apple Remote and Remote Buddy? 
c) Have you tried?

Many thanks. You have an exceptional application and an outstanding customer support. 
Kind regards.