I have just managed to install the Palm Audible Audiobook Player software under the new Garnet VM beta 3. It hasn't worked with the previous versions. So far I have only played the demo files that come with the player. I'll try a full book when I get home.

The player is available here: Install from Mac - Install From Windows

To start it from the command line or Personal Launcher/Menu use:

/usr/bin/gvm/gvm -a ADBL -z 1.5