That doesn't make any sense. If you own Red Hat Enterprise Linux 3 AS ("own" as in owning a licence), you have one year of free access to Red Hat Network, too.
However, if you mean you have just acquired a copy of RHEL 3 AS somewhere, sorry for that, you're on your own then and unsupported. It may or may not work for you to fetch the updates as source RPM packages and build them yourself.
And in case you mean you have one licence only, but want to install on more than one server and distribute the updates to more than one server, too, you're violating your Service Level Agreement with Red Hat.
Different question, different answer...