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Hi gas,
steht in der FAQ:

Is the Maps API available for commercial websites?

Yes, it is. As long your site is generally accessible to consumers without charge, you may use the Google Maps API. For example, if your website is supported by advertising, it likely falls within the terms of the Maps API. Or, if you charge people to place information on your map (e.g., to list their homes for sale), but you list this information on Google Maps on a free part of your site, you’ll also meet the Maps API terms of use.

However, not all commercial uses are allowed. For example:

* Premium websites – If your site is only available to paying customers, you cannot use the Maps API.
* Enterprise websites – The Maps API is not available for use within enterprise or intranet applications.

hier