Well, technically these kind of applications don't violate the TOS because all they do is display google maps in a server window and then they take the locally cached tiles.
There's also an iPhone app for jailbroken devices which uses cached google maps tiles for offline use with the normal maps application. It's really quite handy but not the most practical method (it requires desktop software to download the tiles and to create a database which must then be uploaded through ssh to the iPhone)
Yeah, but you could as well recommend pure unadulterated GWT
Once you're familiar with the concepts and philosophy of GWT, you'll be able to decide if you want to use a framework that builds upon it (there are tons of them and some are really crappy, like ext-gwt)
I'm a frequent contributor in the user forums and I find that GWT beginners only get more confused when they try to use a framework on top of GWT without knowing the basics.
Brain off-line, please wait.