PowerDNS [1] has been doing that under the GPL since 2002, featuring a large number of different backends ranging from simple BIND style zonefiles to relational

PowerDNS [1] has been doing that under the GPL since 2002, featuring a large number of different backends ranging from simple BIND style zonefiles to relational databases and load balancing/failover algorithms. [1] https://www.powerdns.com/ https://www.powerdns.com/