Peter has graciously given me administrator privileges so that I can take this project in a new direction. I would like to announce the creation of libat43usb, a library for the USB functions in the Atmel AT43USB3XX family of microcontrollers. The initial target is the '355 as it is the one on my AvrUpod development board. The current status of libat43usb is pre-alpha; some files exist with content, but nothing can be built yet. If anyone is interested in this project, please subscribe to the maillist.
I've uploaded the messages I got while connecting a 2313 to a USB port.