OK, well I may be a little off beat here but I thought maybe my input (2cents) would help
(after all it's nice to give back, if you can, to a community that helps you)
1) phpchat (free) http://www.phpfreechat.net/
2) ajaxChat (free) https://blueimp.net/ajax/
or my prefered:
3) Code your own, JS, Ajax and PHP/MySQL
Currently I use 3 (which look bad) but we did have a look at dropping it and using ajaxChat instead.
ajaxChat certainly was setup nicer than my home-made solution, but we didn't have the control that we wanted so we continued the home-made solution.
and as a closer, although it's even further off topic and may not be what anyone wants:
a 'bot' / Artificial Intelegence if you wanted to incorporate it into your chat once you got your chat going: http://blog.program-o.com/
(It won't pass off as a human unless you do HEAPS of work, but it makes a fun textual play-thing for your chat's members.
Once I finally pickup where I left off and get tokbox happening again and integrated i'll happily share with you how I incorporated the text chat side of things with the usage of the cam and audio side of tokbox.