Dents is a general-purpose DNS server.
lbnamed is a load-balancing DNS server. Like pickdns, it actively bounces between different answers; unlike pickdns, it gives only one address at a time to each client. The distinguishing feature of lbnamed is that it monitors the load of the target servers and avoids giving out the address of a heavily loaded server.
lbdns is another load-balancing DNS server.
I've heard some reports of DNS servers with client-differentiation features similar to pickdns.
Dents includes a DNS cache.
I don't know why anyone would want to use these caches in place of dnscache.
adns is a stub resolver library.
ares is a stub resolver library.