Since it is working on a Windows machine, I suggest you might want to contact the Docudesk people as to what's going on.
Also, kovidgoyal should be able to help with libprs500 since he wrote it.
The battery status won't change if you charge via the USB port. The battery bug fix needs the power adapter. After it's charged, you unplug the Reader, turn it on, and plug back in the power adapter for about 10 seconds and then unplug it and the battery meter will display the correct status.