Woah, woah, woah. Calm down, Excited Bob: this ain't yer everyday beta. It's a little different, this one - specifically, it's to test the toolset for Bioware's upcoming spiritual sequel to Baldur's gate. The follow-up to the long-lived, enormously successful Neverwinter Nights modding kit, in other words. So it is indeed an early chance to play with the engine, but you'll be making your own adventures rather than carving through Dragon Age's story.
The good news, though, is that they're not looking for veteran modders: rather, they want a range of guys, including total game-fiddlin' newcomers, in order that the toolset really gets put through its paces. If that appeals to you, apply over here and cross your fingers. You'll need to create a Bioware Community account first, however -and that happens here.