After months of deliberation, the global internet standards body the World Wide Web Consortium (W3C) has agreed to adopt a royalty-free policy for patents in its drive for common standards.

Although the decision seems to encourage greater interoperability by slamming the door on vendors' squabbles over licence revenues, the agreement still contains dangerous loopholes, according to experts.

Chairman of the Patent Policy Working Group, Danny Weitzner, said the commitment to royalty-free licensing was the only way to ensure continued innovation in web standards. If the W3C failed to adopt such a policy, then industry would be less inclined to implement its work.

"What concerns us is that work done in a collaborative way could be held hostage by licensing issues," he said. "[In the past] we had a serious situation where patent holdings prevented us from creating standards." However, some commentators suggested that the patent policy did not go far enough, as it contains clauses that could pave the way for the creation of standards based on patented technology.

"Software patenting is an extremely damaging practice, and we do see a problem where firms are awarded broad patents," said Alex Hudson, vice-chairman of the Association For Free Software in the UK. "It is not clear that the W3C will be able to challenge the validity of such patents, and might be forced to work with them."

Another risk concerns the use of so-called submarine patents - patents applied for before or during a standardisation process. Hudson warned that technology that is patent-free when published might "subsequently be covered by a new patent that pops up into existence".

Weitzner acknowledged that there is also a risk that firms may take innovative technology to less restrictive standards bodies. However, he added, "We recognise that there are lots of technologies that require licensing fees ... but these do not lead to a global, interoperable way of doing things. The W3C works towards ubiquitous interoperability."

The move comes at a time when software licensing rights are making headlines.

SCO is currently trying to gain revenue by claiming that Linux infringes its copyrights.