Up2date

up2date is the command used to initialize Red Hat's client for using their proprietary Red Hat Network (aka RHN) to update a machine. The source code for the up2date is GPL'ed, but the source code for RHN is not. Access to RHN used to be free and unlimited, but since around early 2003, Redhat, in an effort to bolster their support revenue, has started doing annoying things like limiting the amount of machines a non-paying user can have registered, or requiring frequent re-registration...etc.

These days, most folks just use yum, or it's GUI front-end yumex.