There’s an error on FileHandler.cs, can’t compile:

Unity is set to build on WebPlayer which is not supported. Build for any supported platform (iOS, Android, Standalone) and it will fix it.

How can I add a GameObject at some GPS position on the map?:

It’s very easy, read the POI section here in the documentation and try the “POI – Demo Scene” to have an example or just use the “dropPin(double lat, double lng, GameObject go)” method in GOMap class.

The basic GPS-Vector3 conversion is just this.
Coordinates coordinates = new Coordinates (lat, lng,0);
gameobject.transform.localPosition = coordinates.convertCoordinateToVector(0);

The map seems to have stopped loading data, why?:

It’s probably because you have cached some tiles with a different layer content than the one you’re using right now. Try disabling the cache (useCache bool on GOMap.cs) and run again, then put the cache back