VOIP is demo app for SimpleVoiceManager - iOS library for GTalk.
The library was created "just for fun" on base of WebRTC and XMPP standards. Google Talk is on the way to Hangout now that would may impact on signalling schemas and some things would stop working unexpectedly.
You should unpack libSimpleVoiceManagerSimulator.a.zip and libSimpleVoiceManager.a.zip before compile the App