I enable maps on my theme (show_map = True), which activates MapQuest tiles (pin in upper right of image). In the themes, this is written in themes/*/templates/index.html during function init_maps(). As of 2016/07/11 the Mapquest tile server is no longer available for open public use without an API key.
According to their announcement, an API key can have 15,000 accesses per month. I imagine you want to set the templates up to require the user to get their own API key or else link to someone else's map tiles.
http://devblog.mapquest.com/2016/06/15/modernization-of-mapquest-results-in-changes-to-open-tile-access/

I enable maps on my theme (show_map = True), which activates MapQuest tiles (pin in upper right of image). In the themes, this is written in themes/*/templates/index.html during function init_maps(). As of 2016/07/11 the Mapquest tile server is no longer available for open public use without an API key.
According to their announcement, an API key can have 15,000 accesses per month. I imagine you want to set the templates up to require the user to get their own API key or else link to someone else's map tiles.
http://devblog.mapquest.com/2016/06/15/modernization-of-mapquest-results-in-changes-to-open-tile-access/