As the culmination of ten years’ work, the Samba Team has created the first compatible Free Software implementation of Microsoft’s ActiveDirectory protocols. Familiar to all network administrators, theActive Directory protocols are the heart of modern directory service implementations.
Samba 4.0 comprises an LDAP directory server, Heimdal Kerberos authentication server, a secure Dynamic DNS server, and implementations of all necessary remote procedure calls for ActiveDirectory. Samba 4.0 provides everything needed to serve as an ActiveDirectory Compatible Domain Controller for all versions of Microsoft Windows clients currently supported by Microsoft, including the recently released Windows 8.
Full article: https://www.samba.org/samba/news/releases/4.0.0.html