A total of 283 registered software patents, including 27 held by Microsoft, could be used as the basis of patent lawsuits against the Linux kernel, according to a study of US software patents.
The study was funded by Open Source Risk Management (OSRM), a company that provides insurance against lawsuits related to the use of open source products, and conducted by patent attorney Dan Ravicher, executive director of the Public Patent Foundation and senior counsel to the Free Software Foundation.
"There is a non-trivial risk of patents being asserted against Linux," said Ravicher, who added that his findings should not come as a great surprise given the broad scope of the Linux project. "The conclusion we came to is not that Linux is doomed and that this is horrible," he said. "It's very similar to the result you would get if you investigated any other software program that's as successful as Linux."
Though a patent lawsuit relating to some piece of open source software is "inevitable", it is unlikely that Microsoft will be the company to launch such a suit according to Jeffrey Norman, a software lawyer at Kirkland & Ellis. "I don't know if it's going to be Microsoft," he said. "There are some PR issues for Microsoft."
Because of their open nature, projects like the Linux kernel are more vulnerable than proprietary software to patent claims, said Norman. "It's much easier if you have a software patent to go through an open-source product and verify that your patent is there," he said.
But a larger problem is that in the relatively young craft of software development it is easy to come up with techniques that, while novel, should probably not be patentable, said Norman, who cited Amazon's patent for one-click purchasing as an example of such a technique. "The novelty is not novelty with a capital 'N'. You're not inventing the internal combustion engine," he said.
Ravicher's organisation, the Public Patent Foundation, which claims that half of the patents issued by the US Patent Office contain no innovation, is lobbying for reform of patent laws, but Ravicher says that efforts like Grokline.net, which is an OSRM-sponsored effort to catalog the roots of the Unix operating system, could also protect open-source software from patent suits.
The patent study, which took three months to complete, involved examining patents that had been held up in court, as well as those that had simply been issued by the Patent and Trademark Office. Using a variety of automated search tools, Ravicher refined his search to 400 patents that had been tested in court and 1,000 that had not, which he then examined to see if they could conceivably form the basis of a lawsuit against Linux.
Ravicher found that none of the 400 court-tested patents could be used against Linux, but that 283 of the 1,000 untested patents pose a potential threat. Twenty-seven of these patents were owned by Microsoft.
Linux ally IBM turned out to own the largest number of patents uncovered in Ravicher's research. Big Blue held 60 patents that could conceivably threaten the Linux kernel. HP, Intel and Novell also held some of the patents in question, Ravicher said.
Ravicher's research did not examine the risk posed to parts of standard Linux distributions that reside outside of the kernel - things like the K Desktop Environment, or the Samba file sharing software - but OSRM intends to study the risks posed to other open-source products, a company spokeswoman said.
The topic of open-source patent risks was raised earlier this month when a two year-old HP memo urging company executives to develop a strategy to protect HP from Microsoft patent lawsuits against open-source technologies was published on the NewsForge.com website.
"Basically Microsoft is going to use the legal system to shut down open source software," wrote Gary Campbell, who was HP's vice president of strategic architecture at the time. "We don't have to exit selling to the open source market, but we need to plan smartly where to reduce our exposure."
Both Ravicher and OSRM declined to identify the specific patents identified in the study. Publishing the names of the patents could make it easier for a Linux customer to be sued for "willful infringement", which could then lead to increased damages in the event of a successful lawsuit, said an OSRM spokeswoman.
Ravicher's study found no patents held by the SCO Group that could pose a threat to the Linux kernel. SCO, which has been at the centre of a number of prominent lawsuits against Linux companies and users, claims Linux contains code that violates its intellectual property.
Jeffrey Norman was sceptical about the effectiveness of such a study, given the vastness of the code in the Linux kernel and the large amount of software patents that have been issued. "I don't think that you could identify all of the patents that were possibly relevant to the Linux kernel," he said. "The only way you could do it was if you were a kernel developer."