Rainer Schöpf of the CTAN team pointed out that there is a new version of the LaTeX Project Public License, version 1.3, http://www.latex-project.org/lppl/lppl-1-3.html. He stated that this version is DSFG compliant, although I could not find this statement on the web site.
The clauses relevant to FOP's ability to distribute hyphenation patterns derived from files under the LPPL seem to be:
[..]
2. Information that is sufficient to obtain a complete,
unmodified copy of the Work.
[..]
Clause 6.d.2 is a bit tricky I guess. The rest seems OK.
IMHO it should be ok to add this to the NOTICE file (See http://www.apache.org/licenses/example-NOTICE.txt)
-- Christian