Did you get that statement directly from Keyspan? I'd be seriously 
surprised if they wouldn't provide OS X drivers for Leopard for one of 
their flagship IR products.

Your Keyspan Remote for iTunes should work just fine with Remote 
Buddy. RB is independant of any Keyspan software.

However, since your post suggests you have problems with the hardware: 
please make use of the Remote Buddy demo version (it's full featured) 
before purchasing to ensure your hardware is working correctly.

Best regards, 
Felix Schwarz