Script no longer works -- but there is another solution:
Digging around online I've found how to export personal documents, with notes included, to Kindle for Mac. Download DesktopUtility, select "Show Invisible Files".
Then copy the .doc file and the .mbp file from your Kindle, using the USB cable, to your hidden Kindle file on your drive, which is Library/Application Files/Kindle/My Kindle Content.
Open Kindle for Mac -- voila!