Samba developers have definitively switched future versions of the software to the GPL v3 licence, which could have a serious impact on companies maintaining software patent covenants.

"After internal consideration in the Samba Team we have decided to adopt the GPLv3 and LGPLv3 licences for all future releases of Samba," leading Samba developer Jeremy Allison said in a note announcing the move.

Samba is networking software designed to allow non-Windows operating systems to connect to Windows using a reverse-engineered version of Windows' own SMB/CIFS networking protocol. The software is central to the connectivity of Linux and Unix-based operating systems in Windows environments, providing file and print services on Mac OS X for instance.

The new GPL is important because of its provisions to improve compatibility with other licences, to make it easier to adopt internationally and to protect open source software (also called Free Software) against recently developed threats, Allison said.

"We feel this is an important change to help promote the interests of Samba and other Free Software," he said in the note.

The Samba team will renumber future releases to reflect the change, with the planned 3.0.26 release renumbered to 3.2.0. Versions 3.2.0 and later will use the GPLv3, and those numbered 3.0.x and earlier will remain under the GPLv2.

The change could be bad news for companies that have reached software patent agreements with Microsoft, since the GPLv3 is specifically designed to thwart such agreements.

"Patent covenant deals done after 28 March, 2007 are explicitly incompatible with the licence if they are 'discriminatory' under section 11 of the GPLv3," Allison wrote. "Samba distributors who have made such patent covenant agreements after that date will not have the right to distribute any version of Samba covered by the GPLv3."

That would seem to include companies such as Xandros and Linspire, which made agreements following in the footsteps of the Novell-Microsoft deal that originally inspired the GPLv3 provision.

Microsoft has said none of its partners in patent agreements are affected by the GPLv3's provisions, but industry observers have begged to disagree.

The switch could also affect companies using Samba libraries, if the program linking to the libraries is licensed under a "GPLv2 only" licence, since Samba will also be using the libraries-oriented LGPLv3, Allison said. "If you wish to use libraries released under the LGPLv3 with your 'GPLv2 only' code then you will need to modify the licence on your code," he wrote.

Programs using a "GPLv2 or later" licence can link to LGPLv3 libraries.

Allison said Samba contributors could continue to submit code in the same way, since the project has always used an option in the GPL that allows automatic migration to later GPL versions.

The team said it will continue providing security updates for GPLv2 versions of Samba as long as the code is widely used, but will develop new features only for the GPLv3 versions.

Allison said he didn't expect the GPLv3's anti-DRM (Digital Rights Management) provisions to affect Samba users.

"We're not aware of any vendor distributing Samba in such a way that would cause them to fall foul of the new DRM language in the GPLv3, but as always, consult legal advice if you have doubts," he wrote.