CustomDNS is a modular DNS server written in Java. It's based on Brian Wellington's dnsjava pacakge, but it adds support for virtual hostnames, SQL databases, and dynamic client updates. You can use CustomDNS out-of-the-box as a clone of ml.org/dyndns.org, or you can use it to develop custom DNS applications.
OpenVISP Admin is a fork of Postfix Admin. Its aim is to provide a unique ISP tool as a Web panel for end users, postmasters, and site administrator to manage their data. It allows site administrators to update amavisd-new values, spam-assassin values, greylisting, domains checks, and sender verification. It can also provide datacenter admins with a central point of access, by having APC Masterswitch configuration and access, hosting access requests, and PPTP access and statistics views.
ext-Dns is a core library, an extensible forward DNS server, and some additional tools designed to create DNS server solutions which are able to do any additional operation at the resolution level (running commands, rewritting replies, gathering stats, and so on), without any limit. It provides a ready-to-use solution in case you want to build a DNS server which takes additional actions at the resolution level in an easy way. That is, its design is focused on allowing people to implement whatever they like when a request is received, freeing them from most of the details which involves handling DNS protocol.