I realize that legal issues, especially with Google are pretty tangled up. However, I was looking at the Google Base new TOS and saw
10. NO RESALE OF SERVICE You agree not to reproduce, duplicate, copy, sell, trade, or resell any portion of Google Base, use of Google Base, or access to Google Base.
The question I have is that if I'm helping a client get their stuff listed, am I "providing access to Google Base"? I would think not, My guess is that the wording above would apply to a front end to access GB.
IANAL, but I'm think you're right. As far as I understood that, it's against Redirect-Services that push the items under their name and then redirect to the real site. As long as you just tell the client how to set up the account and write the export-scripts etc but do not publish the items under your account and then "sell" the redirects to your client, you should be fine.