Hubot - A Chat Bot for your Company

•    CoffeeScript

Hubot is a chat bot, modeled after GitHub's Campfire bot. It is extendable with community scripts and your own custom scripts, and can work on many different chat services.

Digsby - IM + Email + Social Networks

•    Python

digsby is a multiprotocol IM client that lets you chat with all your friends on AIM, MSN, Yahoo, ICQ, Google Talk, and Jabber with one simple to manage buddy list. It is also a social networking tool that alerts you of events like new messages and gives you a live Newsfeed of what your friends are up to. It also alerts you of new email and lets you perform actions such as 'Delete' or 'Report Spam' with just one click.

ch@tr

Ch@tr is (another) chat application for XMPP that connects to Google Talk. The vision for ch@tr is that it will be a hub for email, calendar, and chat, and help focus a user's work - freeing him from distraction and unwanted im's or emails.

Net Pad

GTalk and Facebook chat application written in C++ with wxWidgets as the UI toolkit.

PoshChat

PoshChat is a client/server chat program written in PowerShell. Supports multiple client connections to a single server to chat.

ios - Experimental iOS client

•    Swift

Experimental iOS client. Status: work in progress.

termchat - Chat through the terminal with hack.chat

•    Python

Open source is love. Without the hack.chat project by AndrewBelt deployed here this project would have been a lot more complicated as most of the heavy lifting is done by it.

spinc - Spark In Console - Cisco (WebEx)Spark Client for Linux/MacOS

•    Go

This is a Cisco Spark (now called WebEx) chat client for use in console. Written in GO that works in MacOS and Linux. This client uses about 15MB RAM compared to the official client that uses 500MB - 1000MB RAM. However, this client currently only support chats (not file-share, video-chat etc).