Okay, thanks. With the converter 4.1 posted on the German message board I've tried to convert xdxf versions of the Littré and the Académie française dictionaries available here:
http://polyglotte.tuxfamily.org/doku..._dictionnaires
For the Littré, the converter says "this dictionary is not in xdxf format", and for the other two it says "line xx: unclosed xml tag".
Sigh.