The Google+ social network launched with much fanfare at the end of June. As the 100-day mark approaches, Google is looking to further expand the audience. The search giant is now dropping the invitation barrier and making the service accessible to all users.

In a statement on the official company blog, Google engineering senior vice president Vic Gundotra explained that the site is ready to move from "field trial" to full beta. Google+ has adequately scaled with the growth of the audience so far—it's not clear how many users connect to the site every day, but Gundotra says that over a billion posts have been shared since the launch.

In addition to allowing anyone to sign up for the service, Gundotra also announced other new features that are going to roll out on Google+ over the next few days. The Hangout feature, which enables multiuser video chat, is going to be supported on mobile devices via the native iOS and Android applications. Google is also expanding Hangouts in the browser, offering integration with Google Docs and screensharing.

Alongside these changes, Google is also starting to open up APIs to third-party developers. They have started by enabling programmatic read-only access to public user posts. Not enough functionality is exposed through the APIs yet to support a full-blown third-party desktop client, but it's not a bad start. Google is also working on APIs for Hangouts, which will make it possible for third-party developers to integrate their own services with the video chat system.

In our own experiences with Google+, we found that the granular sharing model helps differentiate the service and will likely give it staying power. It's already off to a better start than Buzz, which was plagued with privacy problems and didn't offer much innovation out of the box.