Custom Chat Room system for Joomla 1.5

We need a custom chat application that integrates nicely into joomla 1.5. In order to conserve bandwidth and increase efficiency it needs to run under a speedy framework (ajax, ruby, etc) and be stable for production use. Here are our requirements: The system will have a free and a paid area. It can be two separate applications, their requirements will simply be different. Free: 1. There are three levels of users - Administrators, supervisors and members. 2. The members, once logged in, simply see a window where they can read and chat with other users. They may not see a list of other users however. There are pretty much two areas, one to write and another to read. 3. The supervisors are the same except that they are allowed to mute members for a certain period of time (1 hour, 6 hours, 1 day, etc). They can also format their text (bold , underline, etc) 4. The administrators have all the power of the previous two but they are allowed to see the list of users and can contact them individually. Paid: Pretty much the same except that only the administrators and supervisors are allowed to talk while the members just watch. Please provide a rough idea of how you will approach this project (what language, design, etc). Unless your previous work involved anything remotely similar, I dont want a list of websites that you "created"