I've DL the kext and the installer helper and will try it out over the weekend and get back to you. I am running retail 10.5.6 with the logitech dongle with the default apple drivers and the Logitech dongle is not seen my OSX. but the keyboard and mouse work - I just got a apple wireless keyboard, and like you, want to get it to work with the dongle.
It's not a connectivity issue as I've been able to pair up the apple keyboard with the LT dongle under Vista. What IS weird is that I have had it working once, and only once last night, where I got the Apple Bluetooth ICON appearing in the top bar and I was able to use both keyboards [Dinovo & Apple Wireless] plus the mouse but sadly when I tested it post reboot it just disappeared and I've been unable to get it back since.
I've also downloaded a utility that allows you to attach commands to mouse buttons ETC [Can;t rememebr what it's called at the mo - I am at work] and this see's the mouse & dongle and allows a probe of the USB stack which see's the dongle.
Bottom line is that there is not a "supported" driver for the LT dongle for OSX which is why it does not appear as a bluetooth device.
Looking at the LT site it does clearly state that the Dinovo combo is not supported for OSX
I'm holding out on the kext if not - I'll buy a 3rd party BT Dongle and use that as well as the logitech for dual boot purposes.