Maybe with ERC + Bitlbee
Not sure about Gvoice, but Bitlbee is great for Jabber/Gtalk. See the Emacs-Fu writeup.
There are many open-source clients like Pidgin interoperable with the various proprietary messaging servers. I don't think it has anything to do with being shady, as it's just interoperability. They would have preferred to have all the users on MSN, but making it interoperable with AIM made it better software. Many users switched to it because it could do a superset of what AIM could.
Another example: http://www.bitlbee.org/main.php/news.r.html
Three seconds in Google shows that there's a Windows version of Bitlbee. The regular version can be compiled and run on OS X, and is probably already in most Linux package managers. Once the service is running, use whatever IRC client you want to talk to it, including Xchat.
You are not alone. I tried searching everywhere possible (HP Store, Preware and the huge Information Library that we call the Internet), and so far it seems like there is no solution. I currently own a Touchpad with WebOS 3.0.4 and I am using a combination of wIRC and Bitlbee to connect to my ICQ, Jabber and MSN Contacts. No idea how to get Facebook to work with Bitlbee though
Related: BitlBee
> BitlBee brings IM (instant messaging) to IRC clients. It's a great solution for people who have an IRC client running all the time and don't want to run an additional MSN/AIM/whatever client.
So basically, you connect to an IRC server (there are public ones listed on the website) which lets you use various IM services. Kinda cool if you have IRC running all the time anyway.
Mibbit works too, so it's not as if you're stuck on freenode. And actually, if you use Mibbit to connect to one of the public bitlbee servers, you've got access to MSN, AIM, ICQ, Facebook chat, Twitter...