OmnomIRC is a fully customizable and open source IRC-style chatbox software, ready to be integrated into your forum or website. Supports SMF, myBB, AcmlmBoard XD and phpBB3!
Have a demo below:
Latest release: 18.104.22.168
Just dump all the files in omnomirc_www into a public directory, visit it via your web-browser and follow the instructions there.