Instead of adding a ?gmapkey parameter to the url, use the data-ex-apikey attribute in the tag where you load the extention.
no need to go to github; it's right here:
Jim, trying to load data from a different site seems asking for
trouble (exhibit's never been particularly good at that); does it
work if you link to your own local copy of the data?
Jay, it's really difficult to diagnose these things without
access to examples. If you can put something on the web, it's
more likely someone can solve it.
Are there any working examples of using Simile Exhibit 3 with OSM? Given the recent announcement from Google regarding the licence and price changes this will likely prove more interesting.
I don't like google conditions very much. I want to write a fork
including osm if I have time next months.