Update 6/21/11: The game just went live on the Amazon Appstore, go get it!
P.S. Unavailable on the Hero and XOOM but available on the Tab 10.1 and EVO? I can maybe understand the Hero, but the XOOM?..
Update: According to the comments, the game should work on devices listed as unavailable - you just have to buy it in the web version of the Appstore and then download as usual within the Appstore app.