well, to use a headset on GW you either have to get teamspeak or ventrillo. Teamspeak is free (www.goteamspeak.com) but I do not know about ventrillo, if its free or website. them you get other people who have same program, and join on a server, while have TS/VENT running in the background
Ventrilo is comprised of two parts: Server and Client.
Server 2.2 - Public version:
The public version of the Ventrilo 2.2 server can be used without a license fee, so long as you abide by the terms of the LICENSE. Each of the public servers contains a file named LICENSE and by downloading and running the server you are agreeing to the terms of this license.
Server 2.2 - Pro version:
The Pro version of the Ventrilo server can not be downloaded. It requires that we accept your application and that you sign and return the Ventrilo license. However, we do not license everyone.