theres a j2me app named mgmaps aka mobile gmaps which used to have google map, yahoo map, msn map and few others. later he recieved letter from google to remove google map service. after that he removed google map option but provided custom map url, now users can add google map url and then use google map now. now the author of the app donot violate any google rule but the user. now the question is is api for those maping sites similar? i mean if user replaces url of osm with url of google map will it work without changing any other settings/codes? if yes then I don' see any point not to allow users to add custom url in your app. i hope this is the case.
[Google Maps] fileFormat=/home/user/MyDocs/.maps/Google Maps/%d/%d/%d.png urlFormat=http://mt.google.com/vt?z=%d&x=%d&y=%0d minZoom=0 maxZoom=20 [Google Satellite] fileFormat=/home/user/MyDocs/.maps/Google Satellite/%d/%d/%d.png urlFormat=http://mt.google.com/vt?lyrs=s&z=%d&x=%d&y=%0d minZoom=0 maxZoom=20