Samba is a free software re-implementation of SMB/CIFS networking protocol released under the GNU General Public License. As of version 3, Samba not only provides file and print services for various Microsoft Windows clients but can also integrate with a Windows NT Server Domain, either as a Primary Domain Controller (PDC) or as a Domain Member. It can also be part of an Active Directory domain.
Samba runs on most Unix and Unix-like systems, such as Linux, Solaris, and the BSD variants, including Apple's Mac OS X Server (it was added to the Mac OS X client edition with version 10.2). It is standard on nearly all distributions of Linux and is commonly included as a basic system service on other Unix-based systems as well.
Samba has a 10-year development history, and as a result Samba-3 is both a robust and mature Enterprise Class project. It has been deployed in organizations small and large as a stand-in replacement for more expensive Microsoft™ Windows® based solutions. Because Samba is freely available under the GPL, it can scale with network environment it was deployed to function in without the need to worry about restrictive per-seat, or per-user licenses.