The patent cross licensing deal unveiled by Microsoft and Novell on 2 November will be incompatible with the GPL3 licence and is likely to be incompatible with the current GPL2 licence, according to law professor and open source activist Eben Moglen.  

Section seven of the current General Public Licence (GPL2) prohibits people or corporations from distributing the GPL code if they have entered into any agreements that contradict the conditions of the licence.

"If you cannot distribute so as to satisfy simultaneously your obligations under this licence and any other pertinent obligations, you may not distribute the program at all," the GPL licence states. 

The provision would prevent Novell from making it mandatory for users to pay a licence fee for its Linux distribution if Microsoft had required this as part of the patent agreement.

Microsoft and Novell unveiled a broad-ranging partnership around Novell's SuSE Linux distribution on 2 November.

The two companies have signed a patent cross licensing deal that will protect users and developers of SuSE against patent claims from Microsoft.

Both companies also vowed to work on interoperability between the two operating systems, and Microsoft will distribute up to 70,000 copies of SuSE to its customers through a coupon programme.

Moglen said in an interview with vnunet.com that Novell should explain in detail how it plans to honour the GPL while satisfying the terms of its licence agreement with Microsoft. 

"Novell needs to show affirmatively that the terms of its arrangement with Microsoft do not impact on the freedoms that they must be able to pass along under the GPL," said Moglen.

Novell has not yet disclosed the exact details of its legal agreement with Microsoft. But company spokesman Bruce Lowry claimed that the partnership does not violate the GPL.

"The patent agreement signed by Novell and Microsoft was designed with the principles and obligations of the GPL in mind," Lowry told vnunet.com. 

He added that the company is working on a document that explains the deal in more detail and will provide a legal background.