This section was written by Joost van Baal.
Various packages exist for getting a DNS server on your box. There is the BIND package (http://www.isc.org/products/BIND/); the implementation this HOWTO is about. It's the most popular nameserver around and it's used on the vast majority of name serving machines on the Internet, around and being deployed since the 1980's. It's available under a BSD license. Since it's the most popular package, loads of documentation and knowledge about BIND is around. However, there have been security problems with BIND.
Then there is djbdns (http://djbdns.org/), a relatively new DNS package written by Daniel J. Bernstein, who also wrote qmail. It's a very modular suite: various small programs take care of the different jobs a nameserver is supposed to handle. It's designed with security in mind. It uses a simpler zone-file format, and is generally easier to configure. However, since it's less well known, your local guru might not be able to help you with this. Unfortunately, this software is not Open Source. The author's advertisement is on http://cr.yp.to/djbdns/ad.html.
Whether DJBs software is really an improvement over the older alternatives is a subject of much debate. A discussion (or is it a flame-war?) of BIND vs djbdns, joined by ISC people, is on http://www.isc.org/ml-archives/bind-users/2000/08/msg01075.html