IRC is still heavily in use in open source development and gaming circles. You can even use it to implement things like Twitch.tv chat.
The great thing with open protocols is that everyone can write clients and servers for them.<p>I&#x27;ve never used Slack but their front page alone is enough for me to turn away. The first two words I see is &quot;Product&quot; and &quot;Pricing&quot;. Nothing on the page hints to an open protocol so I guess it is proprietary.