Open-source leaders have called for a boycott of standards from the Organization for the Advancement of Structured Information Standards (OASIS), in response to a new OASIS policy on the use of patents in its standards.

In an open letter, more than two dozen prominent figures, including Tim O'Reilly, Bruce Perens, Eric Raymond, Lawrence Rosen, Richard Stallman, Lawrence Lessig and Stuart Cohen, said the patent licensing terms allowed by OASIS' policy "invariably and unreasonably discriminate against open source and free software to the point of prohibiting them entirely". The policy will "lead to the adoption of standards that cannot be implemented in open source and free software, that cannot be distributed under our licenses", the letter stated.

OASIS' revised policy, set to take effect on 15 April, allows standards to include patented technology if the technology is available for license under "reasonable and non-discriminatory" (RAND) terms. However, RAND terms effectively exclude open-source software, which by its nature must be free to distribute with no strings attached.

Free/open-source software advocate the Free Software Foundation Europe, for example, has criticised the RAND terms on which Microsoft has proposed to license its server protocols, because they would prevent the protocols from being implemented in key open-source software such as Linux and Samba. Microsoft must license the protocols as part of anti-trust remedies imposed by the European Commission.

The leaders signing the OASIS open letter say standards bodies should stick to truly open standards, which can be implemented with no strings attached, for example through royalty-free licensing.

"Do not implement OASIS standards that aren't open," the letter said. "Demand that OASIS revise its policies. If you are an OASIS member, do not participate in any working group that allows encumbered standards that cannot be implemented in open source and free software."

The letter said the W3C - the World Wide Web Consortium - has the right idea with its royalty-free patent policy, but points out that this was only achieved after a struggle. "Some W3C member companies, steadfast opponents of software freedom, moved their efforts to OASIS," the letter said. "Without consulting the free software/open source community, they produced a patent policy designed so that we cannot live with it."

Contributors to OASIS standards can license their intellectual property under RAND terms, RF (Royalty-Free) terms or under limited RF terms. While the open-source advocates recognised a royalty-free mode exists, they said it is "a secondary option" and argued "a few OASIS members with patents can ensure it is not used".

OASIS has defended its policy, claiming the letter misrepresents the way patents are treated in OASIS standards and pointing out that OASIS standards including royalty-bearing patents are comparatively few. The standards body said it is open to a dialogue with the open-source community, and could modify its policy further in the future.

Some public bodies have attempted to promote the use of open standards through policies excluding the use of standards that contain royalty-bearing patented technology. Such policies can help to lessen organisations' dependence on standards that are tied to particular software - for example, Microsoft Office file formats.

Last week the European Commission published the European Interoperability Framework for pan-European eGovernment Services (EIF), a blueprint for creating interoperable services, which bars standards using RAND licensing. The Business Software Alliance (BSA) criticised EIF, saying it would exclude widely used standards such as GSM. The BSA also said EIF wrongly makes a connection between open standards and open-source software, and is lobbying for the policy to be modified.

Supporters of RAND say royalty-free terms exclude much of the best technology from standards, because it happens to be patented. Most standards organisations, including the IEEE, the ISO, the IETF and the ITU, allow standards to include patented technology under RAND terms, the BSA argued.

Big patent holders have recently attempted to hold out an olive branch to open source developers, with IBM last month allowing the royalty-free use of hundreds of patents for open-source projects. Sun Microsystems followed suit soon after, with patents related to Solaris, and Computer Associates (CA) last week joined in with patents of its own. CA said it is still working out the details of its plan, including the timing and the terms of use.