I'm not sure if you're being intentionally obtuse here, but maps.google.com is the public Google Maps website, while the Google Maps Javascript API lives at https://developers.google.com/maps/documentation/javascript/. The very first page there says:

The JavaScript Maps API V3 is a free service, available for any web site that is free to consumers. Please see the terms of use for more information. ...with a link to the full TOS for the API: https://developers.google.com/maps/terms