Jeremy Allison - Sam
writes "We released Samba 4.0 today, containing the first compatible Free Software implementation of Microsoft's Active Directory protocols. '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 Active Directory. Samba 4.0 provides everything needed to serve as an Active Directory Compatible Domain Controller for all versions of Microsoft Windows clients currently supported by Microsoft, including the recently released Windows 8. The Samba 4.0 Active Directory Compatible Server provides support for features such as Group Policy, Roaming Profiles, Windows Administration tools and integrates with Microsoft Exchange and Free Software compatible services such as OpenChange.'"
Full release notes
are available, and you grab the files from the download page