DOTA2 has been in open beta for a very long time now, but it looks like Valve thinks the game is finally ready for the open market. Hoping to avoid fiascos similar to the launch of Diablo III and SimCity, Valve is trying a graduated release program that will only allow small numbers of players onto their servers at launch. Here is a description of their plan:
If you want to give Dota a try, or you have a friend you want to bring into the community, click the button above and you can get in the launch queue. You'll see your place in line, and when it is your turn we'll send you an email letting you know you're in. We'll begin sending those emails this week
More information about the DOTA2 launch plans can be found on Valve’s official DOTA 2 website.