Hi:
Your Google account password is not stored at all, anywhere -- not on the OBi device, and not on the OBiTALK web portal.
During setup of a Google Voice number on an OBi device, you will first log into your desired Google/Gmail/Google Voice account on a computer's web browser. Leaving that tab open and logged in, you'l then open a new browser tab (Ctrl-T) and then log into the OBiTALK web portal in that second tab. You will then click on the desired Service Provider slot (SP1--SP4 on a 202), and you'll be prompted through the Google Voice setup procedure.
During the procedure, OBiTALK will kick off an OAUTH 2.0 secure (encrypted) token exchange with your Google account. It will ask you to confirm that you are logged into the correct Google account (in the other tab), and then it will take you to your Google account permission page, where Google (not Obihai) will ask for your approval to grant OBiTALK access to the Chat service on your Google account. After that, the token exchange will take place. At no time is your password ever exposed. All you are granting the OBi device is access to the one specific service on your Google account. There is no way to reverse engineer nor sign into anything else on your Google account, as a result of the token exchange. At any point in the future, you have full control over revoking that permission if you wish, on your Google account management page.