a geonames sparql endpoint is planned but not yet available. For the time being you would have to call the xml or json services. Whether this is possible with jena you would have to enquire on a jena specific forum.
I was not aware of geosparql.appspot.com.
GeoNames does not have any maps. The maps you see on this website are provided by google. Check out the googlemaps documentation for details: http://code.google.com/apis/maps/index.html