Will dota 2 be available on amazon

No physical box game has been announced, but you can digitally purchase a beta key invite through amazon. But the game will still run through Steam regardless!
You can have a chance of getting the game without a purchase by just signing up on their site, that's how I got in. Supposedly this game will be free to play with a in-game micro-transaction system for their income. But since VALVe gets plenty of money from TF2 and Steam itself, I believe they can continue to run DOTA 2 with little in-game purchases.