Yeah, the realforce's embedded numpad doesn't work on the mac since it is looking for the numlock light. (Which is stupid... who wants their embedded numpad on just because their PC enabled numlock on boot?)
You can use KeyRemap4MacBook to get an fn key. Just install it and enable the setting "Application Key to Fn" under "For PC Users", "Change PC Application Key". This will make the key between right windows and right control fn.
If you want the embedded numpad to work, you can add
my settings to your private.xml.