Thanks for the kind words, Tom.
I haven't really worked much on this tool since I released it. While I am probably not adding XM or YMZ280B support, i decided to try to implement FM by hacking the MOD format a bit.
Link here, instructions are in the "FM readme.txt". I planned to use this to make VGM rips of the music from Zone 66, but that didn't really go as planned, probably because the conversion from the original sound format to S3M wasn't perfect. (The conversion from S3M to MOD was fairly simple thanks to the song not using any effects, it should have had detune effects but those were missing in the S3M).
Still it should be usable for anyone that wants to make FM+PCM music with the OPL4. Limitations include not being able to use quite all FM channels, and no rhythm mode or 4op support.