As the wiki says:
Contact a sysadmin, the sysadmin will disable your account and remove your details from the OpenStreetMap database. Your email address will usually be retained in the event that an OpenStreetMap sysadmin needs to contact you in the future.
If you have made any modifications or additions to OpenStreetMap, the sysadmin will ask you to license these under any future OpenStreetMap Licenses or to release as public domain.
answered 21 Sep '10, 11:35