On the other server I was on they allowed me to use it, although it does have to use 1 mysql database, and as mentioned above it's a direct chat with me, the site admin. I use the support because my site is a radio station that streams with a shoutcast server. I use the support for issues with my visitors connecting and for music requests when I'm streaming. So I really need a certain answer cause I don't want to loose hosting again because of such a small issue, my other host sold to a new owner without notice so thats why I had to switch.
Since it's not a regular chat script, but rather a two way communication I'd guess it'll be ok. Though it all depends on resource usage.
If it should come to a point where your account use too much resources your account would be suspended, the first two times you can unsuspend yourself, on the third you'll need to contact staff by submitting a support request who then should be able to see what script is causing an issue.