Same here. “No package tac_plus available”. I can also see it in the list. Cannot install it manually, as there are too many dependencies (which is why we use yum. haha)
I, too, am using Centos 6.4. If I do just a yum list, it does not show it.
[root@logger ~]# yum list --enablerepo=nux-misc | grep nux-miscanything-sync-daemon.noarch 3.11-3.el6.nux nux-misc
chronicle.noarch 4.6-1.el6.nux nux-misc
clamassassin.noarch 1.2.4-1.el6.nux nux-misc
cobbler.noarch 2.2.1-2.el6.nux nux-misc
cobbler-web.noarch 2.2.1-2.el6.nux nux-misc
dkimproxy.noarch 1.4.1-1.el6.nux nux-misc
fuse-s3fs.noarch 0.9-2.el6.nux nux-misc
koan.noarch 2.2.1-2.el6.nux nux-misc
megactl.i686 0.4.1-1.el6.nux nux-misc
megactl-debuginfo.i686 0.4.1-1.el6.nux nux-misc
openresolv.noarch 3.4.1-2.el6.nux nux-misc
perl-Apache-RPC.noarch 0.69-2.el6.nux nux-misc
perl-RPC-XML.noarch 0.69-2.el6.nux nux-misc
perl-XML-RSSLite.noarch 0.15-1.el6.rf nux-misc
pssh.noarch 2.3.1-4.el6.nux nux-misc
z-push.noarch 1.5.6-1.el6.nux nux-misc
zarafa-z-push.noarch 1.5.6-1.el6.nux nux-misc