So, I read the locked post:
OBi 100/110: illustrated, step-by-step instructions to use Simonics GVGW
by SteveInWA
Then, I see this:
http://www.obifirmware.com
So do you need to update the firmware or not? Does the second approach bypass Bill Simon's site? Enlightenment please!
The unofficial modified firmware lets an OBi100 or OBi110 function with GV in exactly the same way (using XMPP protocol) that it did before the changes made by Google Voice.
The Simonics GV gateway uses a different protocol (industry standard SIP) to communicate with your OBi device. The Simonics gateway communicates with the Google Voice servers using the XMPP protocol. Thus, provided that the gateway is able to accommodate any changes that GV makes, your OBi device is isolated from them.
The choice is yours.
By using the gateway you can also use other voip clients such as soft phones and android apps (csipsimple, zoiper, Grandstream Wave, bria, etc) directly with your google voice account.
The modified firmware has the added benefit of completely eliminating the need to use obitalk portal to provision the google account. Depending on your needs, each has its own benefits.
For those reading this thread, there's also a similar firmware for the obi200/202 models.
Simon Telephonics costs $6, does not require an OBi ATA, adds Caller ID name, supports more codecs, supports TCP/TLS, and offers fax-to-email.
The third-party firmware is free, and makes your OBi work exactly as it always has. It does not require the Simon Telephonics service.
In terms of making and receiving calls, both methods do more or less the same thing. Start with the free option, and if you decide you want the extra features of Simon Telephonics, you can always upgrade later.