Microsoft is putting on hold the addition of newly licensed open source software code to the Linux distribution deal it inked last year with Novell out of concern that including the new code could force it to abandon key intellectual property rights. In a statement released Thursday, Microsoft said customers who buy from it certificates for Novell's Linux products and services are not eligible to receive updates to the software that are covered by a new open source software license.

The license, General Public License, version 3, was published last week by the Free Software Foundation -- one of open source software's main governing bodies.

New and existing customers that buy Linux through Microsoft's Novell alliance program will continue to receive products and services only for open source software covered by the previous version of the General Public License, GPLv2.

Microsoft and the FSF are at odds over Microsoft's claims that the Linux operating system and some other open source programs infringe on Microsoft intellectual property. In response to those claims, the FSF added to GPLv3 terms that effectively prohibit companies that distribute software covered by the new license from pursuing legal action against open source users.

The FSF contends that Microsoft's alliance with Novell makes Microsoft a Linux distributor subject to the lawsuit prohibition if it distributes software covered by GPLv3.

Under the alliance, customers buy certificates from Microsoft entitling them to Novell SUSE Linux software and services. Microsoft profits from the arrangement as it is effectively reselling Novell's offerings at a mark-up.

In a statement, Microsoft said it does not believe that distributing software licensed under GPLv3 constitutes an acceptance of its terms -- including the prohibition on lawsuits. Nonetheless, the company said it will limit open source software sold and supported through its Novell alliance to code that is licensed under GPLv2, which does not include the lawsuit prohibition.

Microsoft said it made the decision "in order to avoid any doubt or legal debate on this issue."

How the decision will impact large enterprise customers, such as Wal-Mart Stores, that have already purchased certificates for Novell's SUSE Linux through Microsoft -- presumably with the expectation of receiving future updates -- was not immediately clear. Most observers say it's too soon to tell how many open source software developers will migrate their products from the more business friendly GPLv2 to the more restrictive GPLv3.

Linux inventor Linus Torvalds has indicated in Web postings that he's not likely to move the Linux kernel itself to GPLv3.

However, a number of important, ancillary components to open source enterprise stacks could fall under the new license. That has a number of commercial users of open source software worried.

Digital video recorder manufacturer Tivo, for instance, recently warned investors that some terms in GPLv3 could prevent it from offering digital rights management protection to key content partners if the open source software used in its DVR boxes falls under the new license.

Microsoft said it hasn't ruled out adding GPLv3 software to its Novell alliance at a later date. "We will closely study the situation and decide whether to expand the scope of the certificates in the future," Microsoft said in the statement.