From an email from obitalk:
The Google Voice Service is Still Working on My OBi! How come?
At the end of last year, Google Inc. announced that the open and documented XMPP communication protocol would be abandoned in favor of a new, proprietary way to do real-time voice, video and instant messaging communications. The time-line for the migration to this new way was not stated.
At about the same time, but separately, Google stated third-party applications should stop supporting XMPP by May 15th 2014. Now that this date has passed, like you, we have observed Google services using XMPP are still connected and working, e.g. you can still place and receive calls using a Gmail account configured on your Obi device. It is important to note, this does not change the previous statements from Obihai that we no longer support direct connections to Google Voice on OBi devices. We strongly recommend all OBi owners using the Google Voice service obtain a new service to ensure continued, uninterrupted calling from the phone connected to the OBi.
Fortunately, there are several OBiTALK Approved Service Provider (ASP) choices available to all OBi device owners for Internet VoIP phone services. These services are easy to sign-up for and configure automatically on an OBi device. They also come at a great price - with all fees and taxes included.