In a copy of the Linspire agreement published on Microsoft's website, the company said specifically that the agreement doesn't cover "any portions of products that comprise or include Foundry Products, Clone Products, GPLv3 Software or Other Excluded Products".
After the Linspire deal was announced, the Free Software Foundation (FSF) released the GPLv3, which aims to make such patent deals legally impossible. The Microsoft document was published on 5 July, following the GPLv3's release.
In theory the exception means that Lindows users could expose themselves to a Microsoft lawsuit if they use open source components licensed under the GPLv3 and those components infringe on Microsoft patents.
Samba, a widely used networking protocol, has said all its future versions will use the GPLv3, and others are expected to migrate to the licence as well.
Microsoft has told shareholders and the public that it believes many popular open source programs infringe on its patents. Critics have argued, however, that there is little evidence to back up such a claim.
The GPLv3 forbids organizations distributing GPLv3-licensed software to form exclusive patent protection agreements with commercial software developers, and prohibits them from suing open source users.
Linspire and Freespire
Linspire said this week it will release the delayed Linspire 6.0 and Freespire 2.0 Linux distributions by the end of this month. At the same time it will update the Click and Run (CNR) software installation and update system, the company said.
Linspire is the company's paid version, including support, hardware certification and tutorials, while Freespire is available for free.
Unlike most Linux distributions Linspire and Freespire feature broad support for proprietary software and drivers, including MP3, Windows Media, QuickTime, Java, Flash and ATI and nVidia graphics cards.