I still think you're talking about a different, later thing. The client I'm talking about had no plugins and didn't support video, but did support voip directly. It was actually a selling point at the time over MSNM/AIM, iirc. You're right it didn't work on macs, or linux for that matter, because it was a native windows program and they never released a client for any other platform and there was no web interface to it at the time (but you could use any xmpp client with it, as you still can).

I'm pretty sure it was also before google even had TFA.