Nokia's pledge to refrain from using its patent portfolio against users and developers of the Linux kernel is good first step "but is next to nothing", according to a blog entry by Richard Stallman, founder of the Free Software Foundation.

Nokia last week published a document in which it vowed not to enforce any of its patents that are infringed by current official releases of the Linux kernel.

The handset manufacturer also said that it is working on broadening its pledge to other free software projects in which it participates.

However, Stallman, a fierce proponent of free software, pointed out that the Linux kernel is only one of about 4,000 free software projects.

While vowing support for Linux, Nokia is actively lobbying for European software patents, according to Stallman, who considers such legislation a potential threat to open source.

Patents could cripple the open source movement because they allow a patent holder to attack users and developers of open source applications for alleged violations.

Stallman contends that Nokia's limiting its pledge to the Linux kernel proves that the company is planning to use patents against other open source products.

"Nokia is lobbying the European Union to give Nokia and many others a new kind of weapon to shoot at software authors and users," he wrote.

Stallman argues that Nokia should follow IBM's lead, which earlier this year guaranteed the free use of 500 of its patents in all open source projects. IBM, however, is one of the supporters of European software patents.

The potential danger of patents being used against open source projects is not limited to the European legislation currently being debated. Software pate nts are already a reality in the US.

Although there are regular cases against commercial software vendors for patent violations, there have not been any examples of large scale litigation against open source projects or developers.