Several users on the DSLReports VoIP Tech Chat forum discovered how Obihai firmware could be reverse-engineered and updated so that features may be added. The first feature was the update of security certificates on the OBi100/110. Although Google Voice is no longer compatible with 100/110, this third-party firmware extended the life of these ATAs for those who like to use Google Voice. (The 100/110 can still be used with any non-Google BYOD VoIP provider.)
On 19 June 2018, Google decommissioned XMPP servers so OBi100/110 don't work any more, even with the third-party firmware. While it's possible to make the 100/110 work, it's not that easy. If anyone likes to work on this project, please discuss it at DSLReports.
Still are good features in the third-party firmware for OBi2/3, OBiPHONE, and now OBi5. The new firmware allows Google Voice to be configured without the OBiTALK portal. Also adds a SSH server, allows unlocking of vendor-customized devices, allows the OBi3 ATAs to be configured with Google Voice(!), and allows Caller ID contact list.
Not any more. Some very intelligent users developed a firmware that is a direct replacement for the official firmware and can be easily installed using traditional methods.
These firmwares, like the official Obihai firmwares, are provided without warranty. Standard precautions apply, such as do not install firmware over a wireless network connection.
DSLReports hosts one of the busiest VoIP forums on the internet, which is the forum where this firmware was first discussed and published.
The OBiTALK Community is a forum specific to users of OBi products. It has largely been abandoned by Obihai but the users are sometimes helpful.