Actor.OnOff() refers to whether or not the actor representing the light is displayed in the scene, not whether or not the light is turned on. Since Poser's global lights don't display by default, you're getting zero for all of them. As far as I know, there's no way to directly query whether a light is turned on or off. (Unfortunately, you can't access it as a Parameter either.) You would have to use Scene.SaveLibraryLight() and then collect the information from the LT2 file.