Do not put any third party adverts or content that could in any way be said to be profitable from their trademark. However if that stops you ever being able to develop it I would just leave it either not resolving or with a custom parking page where people can contact you easily and directly. It's impossible to say where you stand legally on a domain forum but some things to consider are whether you would have registered the domain *without* them existing in the first place, your reasons for registering the domain, and if you were going to resell it who you thought your target market might be.
