Some companies will not allow certain scripts on their servers - usually scripts with known, unfixed security problems like FormMail. Many also disallow IRC - some disallow any kind of IRC programs on servers within their network.

More and more companies are now targeting people who want to install games on their servers - that's targeting for sales prospects, not targeting to shut them down. Just read over the TOS carefully, ask questions about anything you don't understand, and always look for a dedicated server provider who's good at communicating with you.