Hi David,
I have uploaded a pre-release for you here:
http://downloads.iwascoding.com/downloads/GarageSale_6_2015-06-18.zip
Please note that you have to update your categories in the preferences (even if it states that it is already up to date). With this release you will still get the warning about the not found product, but you should be able to upload listings without a EAN/ISBN/UPC to categories that requires a product identifier. The “Does not Apply” is automatically set on those items.
Thanks,
Paul