ISO is now hosting from their site free PDF versions of many ISO standards, notably Schematron, RELAX NG (full and compact syntax) and NVDL. These are available from the Publicly Available Standards section.
Other free standards available include for C, C# and CLI, FORTRAN, Z, JPEG200, CGM, and many concerned with telephony and removable media. ASN.1 is on the way, too.
I’d like to thank those involved at ISO, both staff and committee participants, for making Schematron and the other standards available free: it is a great step forward.