BIND

Berkeley Internet Name Domain
most widely-used DNS implementation
developed by ISC (Internet Systems Consortium)
http://www.isc.org/

How to get it
ftp://ftp.isc.org/isc/bind/
ftp://ftp.isc.org/isc/bind9/

Recommended version: BIND9
safe, robust, protocol conformance
supporting latest protocol standards
BIND8 may still be okay, but at least drop BIND4