The HexChat program is very similar in form and function to Xchat, except that it is completely free and open source. It works for Unix-like systems and for Windows. The program is an IRC client that is based on XChat, and it is completely legal.
You may have already tried this chat system
HexChat was known as FreaksChat, which then spawned Xchat-WKD. Xchat is a multi-platform chat program, and so is this program. It allows users to join multiple IRC channels, which is what most people refer to as chat rooms. You may talk publicly or one-to-one in chat rooms. The interface is very basic, but that is all part of how chatrooms have progressed. They are no longer popular enough to warrant people creating fancy chat rooms. The upside to HexChat is that it is open source and free, so you may use your own programming skills to make it better and fancier.
There are far worse chatting programs you can choose from
The GUI looks basic, but it does allow you to join multiple IRCs without having to pay for software. It may better suit people who have their own group that they would like to communicate with for whatever reason. It is probably better suited for people who have the programming skills to make the software more sophisticated and good looking.