g4jsf is not about the Google Map component, but about Google Web Toolkit (GWT). If you need only the map, there is no reason to use g4jsf.
Take a look at http://livedemo.exadel.com/a4j-jsFunction/
This example show how you can able to use pure Google Map Widget and Google Map API to integrate Google Map in your JSF application. There is only facelets are there, but it should work the same way with Seam as well.