PeepSo Chat Addon GPL Overview:

Communicate via private messages & real-time chat. Every community needs a convenient way for members to message each other privately. This plugin adds private messaging and also the possibility to create private group messages between many members.

PeepSo Chat Addon GPL Features:

• Real-time Chat
  Chat works in real-time. Always.
• Resource Friendly
  Chat has been optimized for minimal server usage.
• Onsite notifications
  Real-time onsite notifications.
• Email notifications
  Users will be notified by email when there’s a message waiting for them.
• Group chat
  Chat and Messages work with one-on-one or group conversations.