If you are just changing the registrant, admin. tech or billing details the owner of the domain can do that from the registration panel>modify whois. But it will still remain on the other persons account so you may have to do a joint support request to have it moved it from one account to the another.
Then once it is moved you can change the whois, if you want, from the privacy whois to your own whois details.
The other person may have to quote the security code next to the domain in his list of domain(s).
Opinions are my own views, not DreamHosts'.
I am NOT a DreamHost employee OK!! :@
You act on my advice at your own risk!