You might want to ignore all of this, as I haven't touched it in ages. I used GroupVoice in Call of Duty 2 (for PC voice chat) and CoD4, but heavily modified and I'm not going to roll the changes back into it, as they're now owned by Activision.
  • GroupVoice - (BSD License) - A team voice chat library meant for multiplayer games. It is available under a BSD license.