I found another solution with jsonp which does not required the proxy. I got the snippet from https://plus.google.com/107699016136236175558/posts/UjeobQpnLkm and pastbin http://pastebin.com/aADiuQHm. Further it uses the nominatim service from openstreetmap which is the official OSM name to geo service.

Code: 

function jsonpCallback(response) {
}
function geolocate(queryString) {
  $.ajax({
    url: "http://nominatim.openstreetmap.org/search",
    dataType: "jsonp",
    jsonp : "callback",
    jsonpCallback: "jsonpCallback",
    data: {
      q: queryString,
      format:"json",
      polygon: 0,
      addressdetails: 1,
      json_callback: 'jsonpCallback'
    },
    success: function( data ) {
      if (data && data.length > 0) {
        var foundPosition = newLonLat(data[0].lon, data[0].lat);
        map.setCenter(foundPosition, 16);        
      }
    }
  });  
}