<esri:Map id="map" logoVisible="false">
<layers:KogisLayer id="kogisLayer" url="/myapp/servlet/com.esrifrance.kogis.server.KogisServlet?" />	
<esri:GraphicsLayer id="graphicsLayer" />
</esri:Map>

function reallyHideESRILogo(map : Map) : void {
  for(var i : int = 0 ; i < map.numChildren ; i++){
    var component : UIComponent = map.getChildAt(i) as UIComponent;
    if(component.className == "StaticLayer")
       for(var j : int = 0 ; j < component.numChildren ; j++){
         var stComponent : UIComponent = component.getChildAt(j) as UIComponent;
         if(stComponent.className == "Image"){
           stComponent.visible = false;
           return;
         }
      }
  }
}