entOS is a repackaged version of Red Hat Enterprise Linux. The CentOS team is a volunteer group that repackages publicly available RHEL source packages into binaries. The software is then distributed through various public mirrors. To my knowledge, there is no direct relationship or partnership between CentOS and Red Hat. The lack of this formal relationships has created problems in the past, such as a when Red Hat demanded all Red Hat branding be removed from CentOS.
h3. No Official CentOS Support