That zip file contains a different firmware file than is currently available publicly at http://jetbook.net/upgrade.php
. It might be possible to drop the firmware file in "your" zip into the directory structure of http://jetbook.net/upgrade/JL08-v015d-b.zip
and try the upgrade. I personally am *NOT* willing to do the experiment.
As an aside, my jetbook came with firmware v0.15, so I held off upgrading to v0.15d-b for a while. When I did, I was pleasantly surprised that some PDF table of contents were now supported. I can now jump directly to chapters and sub-sections in many of my PDFs. I hadn't seen that mentioned elsewhere.