Remote Buddy currently does not support free button mapping in Leopard 
Front Row as Leopard Front Row presents a complete change from Tiger 
Front Row:

It no longer uses iTunes for playback (=> no ratings, no iTunes volume 
control make sense any more), it will prevent any window from 
displaying on top of it (including Remote Buddy's, so opening Remote 
Buddy's menu will work, but not be visible - and I've received many 
claims of "Remote Buddy doesn't work" because of this as of course, 
when the menu is open, you control the menu, not Front Row - just 
Leopard Front Row will prevent the menu from being displayed as long 
as it's active).

Best regards, 
Felix