IRC, or Internet Relay Chat, is often used as a real-time communication capability with open source projects. Apache Tajo team also uses IRC to immediate communication. You can ask questions or talk about all things Tajo to the channel. Tajo channel is at:
IRC software can be found for all operating systems. The IRC clients comparison chart on Wikipedia can help you pick one for your operating system.
You don’t have to have a complex setup to use IRC. You can use the web client for Freenode, which doesn’t require any download or setup. Just pick a nickname and join #tajo via http://webchat.freenode.net/?channels=tajo.