It's just kerberos/hesiod/afs/moira/etc. plus zephyr, third-party client, config files, etc. That doesn't even count as "installing other software", really. Oh, and cross-realm keys with any site you want, etc.
(I guess you could run Zephyr with somewhat less than that, and maybe it has improved in the past 15y for small deployments, but, when I tried in 2001 it was insane)
