this is the OLD rhel5 ( and the old 5.8 )
you are paying redhat a lot of cash every year to LOCK this at rhel5.8 instead of upgrading to rhel5.10
contact redhat tech support
you are paying for it in the required support contract
yum install vsftpd
will install "vsftpd"
it is in the RHN repo that you have access to with the support contract