[Storebror]

The FM itself basically has got nothing to do with Java, it's just some kind of encryption being applied to a text file which again basically looks like an "ini" file format wise.
The tools being used to decrypt/encrypt the FM(s) are publicly available in Java Archive format, but they could be made in other ways as well.
Furthermore, there are (unofficial/closed circle) mods out there which enable you to use the unencrypted, plain text FM files, but that's another story again.

Best regards - Mike