en fait selon le site de mapquest:
source : http://developer.mapquest.com/web/products/open/mapCitation:
Terms of Use
The MapQuest Open Tiles are available for use for free under the following conditions:
If using the MapQuest-OSM tiles, OpenStreetMap must be given credit for the data – see this section of OSM's legal FAQ for details. [...]
donc c'est bon pour peu qu'on respecte le fait de citer la provenance des images.