Yeah I'm afraid most of the packages I know about are Windows only...I'll let some others recommend them as I've been out of it for awhile.
However you can easily set yourself up - you will need a connection from the earphone out of the 106 to the Macbook (does it even have a 'line in' or 'soundcard in'?) . If you can hear your scanner thru your Macbook speakers clearly without distortion or noise, you're halfway home.
Keep in mind that there's a very short data burst (I think it's 100ms long) that most all decoders need to hear, or you won't get any decodes. Many scanners squelch just doesn't open up that fast, so if you find you aren't getting any decodes, and everything else seems OK, open up the squelch so you hear the background noise.
There is a open source program called acarsdec on sourceforge. Runs from the terminal. I compiled it from source on a linux machine. Since the mac os is a nix variant it may work. You will need apples xcode toolkit to build from source and any other dependencies that program requires.