TabletMagic is an open source driver that allows Mac OS X to communicate with older model Wacom tablets with a serial interface and TabletPC digitizers.
Supported tablets include the UD, UD-II, ArtPad, and ArtPad-II (ArtZ-II) models. This is an ongoing open source project to bring full support for all serial Wacoms. See the accompanying documentation in the download for details. Source Code is available.
MACPERSON0852 Version 2.07b works superbly on my Intel macpro with my old UD 12 tablet and keyspan USB to serial adapter, I even wrote this review using Inkwell!
The software still lacks some features ofered by the Wacom softwarer and required a little adjustment of the settings beffore I was happy, but this is still beta software and as such works extremely well.
Aftcr upgrading I had a problem with the deamon hanging but restarting appears to have fixed this.
Considering Wacom's lack of support for non USB tablets, this is a godsend. (Version 2.0b7)