What is Zentyal?
Zentyal is a native Microsoft Active Directory implementation on Linux incorporating all the network services required in a small and medium business environment: Directory & Domain Server, Mail Server, Gateway and Infrastructure Server.
Comments and Reviews
Said about Zentyal as an alternative
Both NethServer and Zentyal are similar systems. Both are AD servers with lots of similar optional functions. Neth is based oc CentOS, Zentyal on Debian/Ubuntu
Intended to be a full AD Server alternative
It's free and easy to use.