In general, we are not against chat systems for customers.
1) If you run your own service, you would need a dedicated IP address so that you don't get your service "cleaned up" and killed off (search the forums for discussiona about how this works).
2) we generally don't allow java simply because it is a resource hog no matter how little traffic you have. Having said that, people run it occationally, but usually find a better way after their trials and errors.
3) With a dedicated IP, you are allowed to run a bot to sit on irc. Make sure they tag a note on your account that you are going to do this so it doesn't get "cleaned up" by a well meaning admin trying to discourage the occational script kiddie. And yes, occationally accounts get compromised through cross site scripting in free applications, and the kiddie gets access to that account. We clean those up whenever they show themselves.
4) ircd is generally discouraged as it can require quite a lot to setup and get working right. More important, it seems to be a magnet for the script kiddies mentioned above, and becomes a target more often than not.
Principal Systems Administrator