I am not a Mac guy, and I've never used your software, but since you're not getting any other answers, I'll take a stab at it....
When you say the program is "registering" your keyboard. What exactly do you mean by that? I assume that you mean that the program (Logic) sees midi data in response to you pressing the keys on the midi controller?
And then, I'm assuming that you are using Reason as the synth you want to control? If the program is seing midi data being transmitted, but you get no sound, then either the program is not responding to the midi or something in your audio routing is messed up.
A couple of things come to mind-
Make sure that Reason is setup to be looking at the same midi channel the Radium is transmitting on. So if the Radium is transmitting on midi channel 1, than Reason should be receiving on channel 1.
Make sure that Logic is looking on the proper midi channel, too, and that it is set up to accept the Radium as a midi input source
Make sure that you have a patch (sound) selected. In other programs I have worked with, you would select a track to work with (within Logic), assign your instrument to it (in this case Reason is the instrument, and you would select a sound according to however it's done within Reason).
One way to narrow the problem down would be to arm (set to record) a track in Logic, hit record, and play something on the keyboard (regardless of whether you hear any noise). Stop the recording, then go back to the Logic track you just recorded and see if it contains any midi events. If it does, then your problem is most likely within Reason and not Logic.
I wish I could help your better, but, like I said, I've never used either of the programs you have, so what I've just told you is based on knowledge that is pretty generic. It should all apply to your stuff, though...... ;)