PowerDNS is a DNS server capable of IPv6 transport and record resolution. It is GPL-licensed but also available with commercial support. It has a modular design allowing various backend data source modules such as MySQL or a modlue that reads BIND-style zone files.
The main server responds authoritatively to resolution requests but can also act as a forwarder if so configured.
The pdns_recursor component is a standalone caching recursive resolver that accommodates AAAA record types and IPv6 transport. However it will not forward recursive requests to other servers like BIND's forward configuartion, dnsmasq or djbdns's dnscache. So currently one cannot, for example, install this locally and forward all requests to SixXS's resolvers.