Team Speak is free :/...you know...Completely free.
May i quote... from this page here.
http://www.teamspeak.com/?page=faq&cat=sales#who_needs_to_payNon-Profit Organizations
If you host a TeamSpeak server strictly for non-profit AND you are not a commercial entity then you will not be subject to licensing fees. You must not exceed a total of 1000 slots on a maximum of 10 TeamSpeak servers within your organization. TeamSpeak servers are defined as ANY server upon which a connection is allowed - be it virtual or physical.
Examples of non-profit entities:
An individual hosting a single TeamSpeak server configured to allow up to 100 slots for their online gaming clan for non-profit.