I (and other Red Hat admins in the know) run Buchan Milne's alternative which comprise discrete, patched db-4.2.52 and can exist beside the RHEL5 offering. This is an utterly stable and dependable product; it is available at http://staff.telkomsa.net/packages/rhel5Server/openldap/.
Will I have to remove my current db4* rpms to install these ?
No. Buchan's RPMs "can exist beside the RHEL5 offering" after all.