W3C Patent Policy Framework, Section 2.2: it is especially important that the Recommendations covering lower-layer infrastructure be implementable on [a royalty free] basis.

Jeffrey Zeldman points out

There’s no way of knowing … is HTTP part of the lower-layer infrastucture? Is HTML? What about XML and CSS? For the community to buy into RAND, W3C needs to spell out exactly which technologies are and will remain Royalty-free. Otherwise, it’s open season for corporate lawyers to exploit W3C’s vagueness to their companies’ financial advantage.