Rated 3 out of 5 stars
It needs to point to <thesaurus.com> I installed this on a default FF52 profile and it pointed to the defunct address. I was able to work around by changing all references to <thesaurus.reference.com> to <thesaurus.com> in the old XML file: "thesauruscom.xml" (still available, google it). I then used the "XML Search Engines Exporter/Importer" addon to import the XML file to the search.json.mozlz4 file. Works like a charm. If it gets updated I will change the 3-star to a 5-star.