According to the "For the past several months, access to Dota 2 has been granted through a queue system that gated entry into the community. We’ve used this system to gradually increase the size of our playerbase, as we ramped up our infrastructure and improved the experience for new players. As we have recently completed a set of server management upgrades as well as released a huge number of enhancements to the new user experience, we’re going to remove all restrictions to playing Dota 2.,
Signups are no longer required to access the game, and we encourage everyone to join the 6.5 million active monthly users currently playing Dota 2. If you have a friend who hasn’t tried Dota 2 yet, be sure to take advantage of the new recruitment feature to get additional bonuses for both you and your friend."
It's not surprising that the gate has been removed, thanks to the enormous success of microtransactions in the free-to-play game, and making the game easily to get into will bring an influx of more players and income.
Gamers interested in DOTA2 can go to the Steam and simply click "Play".