In 2009, I worked for a company that was developing a modified version of Ignite Realtime's Spark IM client and I have vague memory of sending messages to Gtalk from it. Because of Google's support, XMPP was all the craze back then.

It's great to see that Openfire (Ignite Realtime's XMPP server) has had a release even last week! https://www.igniterealtime.org/projects/openfire/