You need to request a key for "localhost". It's free, so take the easy way out and get a test key.

 
Nancy
Injustice anywhere is a threat to justice everywhere. -- Dr. Martin L. King, Jr.


From: Bert Van Kets

I have been asked to make changes to a Drupal 6 site that was _not_
developed by me. To make sure the changes don't break anything I want to
set up a local copy of the site.
The first thing I need to do is remove a Google Maps install. This is
done using modules and not in the theme files.
When starting the local copy the Google Maps script tells me I need a
new key and then throws me to the home page. I can log in as admin, but
the message for the Google maps key keeps popping up and throwing me to
the home page.