As Tumblr user Buddyp450 points out, signing up for the newsletter at the bottom of the Scrolls game site includes the choice to "opt-in to become alpha tester." Of course, if you're all anti-newsletter or something, but you're one of the hundreds of thousands who purchased a Minecraft license when that (still unfinished) game was in alpha, you're also guaranteed access to the initial Scrolls preview.
Of course, if you miss out on the alpha test, there's always the free public beta after that. And, we imagine, eventually you'll even be able to purchase the full, complete game at some point.
