You "can" run 2D & KR at the same time, by bypassing the KR patch server (won't tell you how, but you can probably figure it out), but it lags even a modern system so bad that the only reason you'd ever want to do so would be to transfer a pet (or rez one) between accounts if you have multiples, or to add people from one account to the other's guild. And those can be done more above-board by logging into two different Windows Identities, logging into UO with both, then switching between them, whereas there's never been an official ruling as to whether the method I first described is legal or not (and the drawbacks are such no one will ever use it for anything other than those limited applications).
Everything else can be done by leaving stuff in ones house (one can add friends & co-owners with 2D alone by logging the character out outside the house, then logging the owner account in and targeting them)
