Neither the term "elementFormDefault" nor the term "unqualified" appear in the DFDL Spec. So we're silent about whether these are allowed or not in DFDL schemas.
We should specify what of this XML Schema behavior is allowed, which I believe means add a line to each of the lists in section 5.1 of things used and not-used/reserved from XML Schema.
FYI: Today the Daffodil implementation implements elementFormDefault on the xs:schema but not the form attribute on element declarations. We have tests that exercise elementFormDefault in qualified and unqualified and not specified at all (which defaults to "unqualified" behavior in XSD, so we're consistent with that.)