As for building a GWT version of Google Maps... yes, you can do that. I am presently working on a GWT widget caller ViewportViewer that works just like Google Maps, including panning, zooming, etc. I started it just for fun a week or so ago. I will likely post the code to my GWT Sandbox site in the next week or two as-is. If I ever finish it, I will add it to the GWT Widget Library project.