Directory+ theme allows you to replace Google Maps with free alternative OpenStreetMap.
Provide of map can be changed under Theme Options > Maps settings. Simply select OpenStreetMap provider and GoogleMaps will be replaced with OpenStreetMap.
For now, OpenStreetMap provider is available in Header Map Element and on small map displayed on Item detail page.
Features availability with OpenStreetMap
No all Google Maps functionality is possible to implement with OpenStreetMaps provider, so you can still use also Google Maps API Key in your Theme Options to use advanced featured like Get Directions, Google Streetview or Advanced Search with real time search through addresses powered by Google.
OpenStreetMap will be still used in Header Map element to save your expenses for loading Google Maps, Google will charge only requests from advanced featured like Streetview, Get Directions functionality or Advanced Search.
Advanced Search functionality working with OpenStreetMap provider too, with difference that there is no available dropdown with addresses to select one, but address is searched by OpenStreetMap few seconds after you stop typing into Location search field.