FOP people say that it's possible to convert a TeX hyphenation file into a FOP hyphenation file, but I don't find how to do it. Is there anybody having done the job for dutch? Please post the nl.xml file.
You can find it in FOP 0.20.3. It was removed in higher versions because there are licensing restrictions that the FOP distribution could not respect. So I can't post it here. You have to download it from an Apache mirror.