> How do we download from his shared drive? Invite only? Secret?
As far as I know the drive is used to share scanned artwork that needs to be restored with those that are willing to contribute in the restoration activity. I upload finished/new artwork so that he can later add the required cfg files to be used with Mame and publish these on Mr Do's Mame artwork site.
About the drive or about when these new artworks will be published I would suggest you ask MrDo directly.