greetings. the open source vent alternative we've decided to try is called mumble (client) / murmur (server). it is similar to vent, except it's free and it doesn't have any limitations.
you can download it here:
http://mumble.sourceforge.net/
you'll want to get the 1.2.2 (stable) version for whichever os you're using.
for the installation, you should only need the mumble (client) box checked, as we shouldn't need backwards compatibility.
when configuring the sound card, most the of the default setttings should be fine. you can set a push to talk key if you want, and don't need to send usage statistics unless you want to.
the certificate creation isn't very important, you can just have it create one automatically.
when the server window pops up, you'll need to add our new server, which is provided courtesy of mike / fargol / heimlorn. the address and login information is in the guild info in game.
upon connecting the first time, just click yes on the certificate error, and then enter the password.
i haven't played with the settings much yet, or actually talked to anyone, but i think this should work ok.
please give it a try and see what you think. if you have any issues with installation, or this alternative in general, please let me know. thanks!