Got version 1.6.020 from the following TomTom support website
This gives ability to operate GO 510/710 from the computer just like windows versions.
That link didn't work for me, but I found version 1.6.020 here:
http://www.tomtom.com/updates/home_16_mac/TomTomHOME_1.6.020.dmg
However it doesn't seem to offer any new capabilities for my 920T. If I click on the "My Go 920" icon I get a screen with a picture of the GPS and the error message: "At this time there is no component available that is compatible with your TomTom device."
So maybe this version allows the older TomTom's to be operated, but not the newer ones?