I would like to take over the hosting of a domain that is currently hosted by another Dreamhost account. The domain in question is not registered through Dreamhost and I have no wish to transfer registration or ownership to myself. How do I go about doing this?
Submit a ticket to Support. As long as the destination account was not set up with a promo code, DH will migrate it over for you.
There is an excellent wiki article on how to do this. This is something you do yourself (with the exception of handling lists, which DH will do for you). You can find the step-by-step guide at http://wiki.dreamhost.com/Move_Domain_Between_Accounts
–DreamHost Tech Support