While Novell investors may be cheering the Linux vendor's partnership with Microsoft, but Linux advocates have an entirely different reaction, expressing concerns that the deal may hint at future patent lawsuits and possibly even violate Linux's software license.

Microsoft and Novell have agreed to work together on marketing and development of their respective products and pledged to make it easier for Windows and Novell's Suse Linux to co-exist in the data center.

But, included in that announcement is a patent cross-licensing agreement that is raising concerns. As part of the agreement, Microsoft has said that it will not sue non-commercial Linux developers and users of Suse Linux, but some worry that this move leaves the door open for the company to sue other Linux companies or even Linux users.

"This is actually bad news," said Bruce Perens, a well-known Linux advocate. "It sets up Microsoft to assert its patents against all commercial open source users. The deal is going to be, 'You have to buy Microsoft-licensed Linux distribution from Novell or there is an implicit threat that Microsoft will assert their patents against you."

Perens even questioned whether Novell's patent agreement might violate Linux's software license, known as the GNU General Public License (GPL), which prohibits Linux distributors from obtaining exclusive patent licenses.

Microsoft has structured its deal with Novell to avoid any conflict with the GPL, said David Kaefer, Director of Intellectual Property and Standards with Microsoft.

While advocates like Perens and Jones may be concerned with the Microsoft deal, Linux's best-known spokesman was sanguine. "I prefer to be an optimist, and will happily take the option that not everybody needs to be enemies," said Linus Torvalds, the creator of the Linux kernel in an e-mail message. "Let's see how it all pans out."