djbdns is quirky dns software useful in some special cases.
It provides various tools and the follow servers:-

tinydns, an authoritative server
dnscache, a dns cache
rbldns, a specialist server for hosting DNS-based lists of IP addresses
walldns, a specialist server mapping 4.3.2.1.in-addr.arpa. to 1.2.3.4 and
vice-versa.
