Nabble's T&C are designed to protect Nabble from anything you or your users might do so, obviously, you and your users are bound by them, so it could be appropriate to include a link to them. It is then up to you to add further rules which define how your forum is to be used. Typically, they might include statements about the range of acceptable topics, how personal abuse will be treated and whether registered usernames take any particular form, for example, some forums might require that real names are used rather than anonymous pseudonyms.
Unless, your forum is one aimed at a business market, where people's profits or income is at stake, or it covers topics likely to slander or libel people, then it is highly unlikely that anything as formal as "terms and conditions" will be required. Most forums are just places for friendly conversation and swapping ideas and information and suing won't be on anyone's mind.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.