This is similar to
DFDL-660, in that I believe this validation error is preventing 'acceptable' namespaces from working.
According to this, ':' should be acceptable in namespace names, both as the starting character and any other character. However, when I try this, the test fails with:
[info] org.xml.sax.SAXParseException: Element or attribute do not match QName production: QName::=(NCName':')?NCName.
Also, should we be able to use XML character entities in namespace names? I believe it should be allowed but I get the same error as above when I try it.