The problem with the iframe approach is that Google's geocoding service TOS explicitly states that the output of the geocode operation can only be displayed on a Google map.
Google's geocoding service is underpinned by a lot of third party datasets which would have to be (very expensively) relicensed if Google started passing the results out to maps under the control of other organisations.
Google's geocoding service is underpinned by a lot of third party datasets which would have to be (very expensively) relicensed if Google started passing the results out to maps under the control of other organisations.