When I saw that you were passing in the stage object (ie: Flash's top-level display container) to the SDK, I assumed it was to be used as some sort of display parent (eg: for a QS game overlay). Reading the documentation & source for SdkFactory cleared up my confusion, but if you're just going to use this object to grab the URL of the Flash window, I'd suggest removing this and only giving the option to provide an explicit URL string instead (whereas now one can either give a DisplayObject or String). Otherwise, saying that users can "pass in any DisplayObject" might create sadness down the road if the loaderInfo for a display object either is different from the main SWF or doesn't have the "qsCanvasHost" parameter passed in (eg: if loading display objects from a dynamic source).

Alternatively, just require that the DisplayObject passed in be a "Stage" object... that way you're sure that they've given you the top-level container for the game window.