"You may recall that at one point Broken Age was planned for release under the Steam Early Access program," Double Fine wrote in a backers-only update on Kickstarter. "This is no longer the case. For various logistical reasons, and because we believe Act 1 is a polished and satisfying piece of content in its own right, Broken Age will be a standard Steam release that includes a 'Season Pass' granting access to Act 2 once it is complete. Anyone who has Act 1 – either by being a backer, or by buying the game separately – will receive Act 2 as a free update when it's ready."
Double Fine announced in July that it would launch Act 1 on Early Access, intending to raise enough money to complete and release Act 2, but a season pass launch can achieve the same end. Backers of the Double Fine Adventure Kickstarter have access to Broken Age Act 1 today, distributed via Steam keys on the Humble Store. Act 1 requires Steam to download, though once Act 2 launches, a DRM-free version will hit Humble.