Caching DNS servers
BIND 9 is a complete rewrite of BIND, and, as such, probably does not have the security issues that previous versions of BIND has. In fact, one of the BIND developers found a security problem in earlier versions of MaraDNS. Very full-featured, and is the reference standard for the newer DNS RFCs.
PowerDNS is an authoritative and recursive DNS server with support for, among other things, SQL. I would like to applaud the PowerDNS developers for making a libre release of this software.
pdnsd is a recursive caching DNS server. Paul Rombouts is the current maintainer of this program.
Posadis is another DNS server project, similiar to MaraDNS. This server is now both a resolving and an authoritative DNS server.
Non-recursive DNS servers
NSD is an authoritative-only DNS server which is compatible with BIND zone files.
MyDNS is an authoritative-only DNS server which uses MySQL as a database back end.
SDNS is a project written in the late 1990s by Sandia Labs. Like MaraDNS, this project was written with security in mind. Since this is a government project, the code is public domain. The program does not seem to be downloadable anywhere, so I am mirroring it here. I would like to thank Fred Cohen for informing me about this package.
The Pliant language/package comes with a DNS server. This DNS server can not recursively process DNS queries given a list of root servers.
Twisted includes a non-recursive DNS server.
DnsJAVA is an authoritative-only DNS server written in Java.
The Eddit project includes a DNS server
SheerDNS is a simple non-caching DNS server that stores all records as their own files.
Abandoned DNS server projects
These are DNS server projects which have not released any files for a significant period of time, and are not fully functioning DNS servers (either because the program did not have basic DNS functionality when abandoned, the program was not documented before being abandoned, or because the program was abandoned so long ago that it is not fully functional on today's internet).
Oak DNS is a DNS server written completely in python. It is compatible (I think) with both BIND zone files and cache files. The file can be downloaded here, here, or here. The most recent alpha version can be downloaded here or here. The most recent file in this alpha is from February of 2003; until this program has a more recent update, I am marking this abandoned. (Thanks, Michel Talon, for the update)
MooDNS is another DNS server project. A CVS checkout on January 21, 2003 shows that no files have been updated since July 20, 2002, except for a single readme file updated on August 1, 2002. This project is abadoned.
I have made a tarball available for people who do not want to bother with a CVS checkout.
Dents is a DNS server that showed a lot of promise. Unfortunatly, no files have been released since 1999.
Yaku-NS is a DNS server geared towards embedded systems. According to the changelog, no one has made any changes to this software since Feburary, 2001.
CustomDNS has not released any files since the summer of 2000.
DjbDNS DJ Bernstein's DNS package, which has both an authoritative DNS server and a caching nameserver. No updates for over five years; however, DJB has very recently (December 28) made DjbDNS public domain, so it's now possible for someone to make an updated release of DjbDNS. I may even do this myself (the software has one bug which I feel is critical, needs a bit of patching to compile in modern Linux distros, and three other bugs that should also be looked at). There are a lot of 3rd-party patches for DjbDNS available at tinydns.org.
Other
LdapDNS is a small DNS server which converts DNS requests in to LDAP requests, without caching.
DnsPython is a DNS toolkit for Python.
GnuDIP is designed for dynamically assigned IP addresses.
JD Resolve is a tool written in Perl that uses DNS to resolve hostnames.
Dproxy is a caching DNS proxy.
No, I don't really care to list every single DNS server that exists here. I find the idea of using proprietary software for anything that matters repulsive; however I try to keep this list up-to-date
QIP These people are obviously hiding something, since they require a password to look up the technical details of their product.
Simple DNS plus. Only available for Windows.