unbound is a resolver, which I think is a bit different from this. unbound's NLnet Labs also make NSD, which is their authoritative server, and that is one of the servers mentioned and compared to on YADIFA's site.
Re:Yadifa, new name server by .eu
by mcpherrinm on Tuesday July 03, 2012 @03:23AM
(#4192952)
While unbound isn't entirely on topic, I thought I'd mention that it will possibly be used in Firefox in the future. https://wiki.mozilla.org/Necko/DNS/ResolverIntegration
The cool thing is that you can hook into the resolving chain with C and/or python.