Chrono Cross Fieldscript is the 4th (i.e. 0003) file (lzss-compressed) in every organized room archive (cpt).
Fieldscript Decompiler is actually opcode-decoder that provides an ability to easily read and edit script files which are then can be compiled back to byte-code and used in game.
This work is a partial rewrite of similar projects — which were bugged/undone or were a part of bigger application.
No one will ever remember a full list of possible authors or even resources they are lived in, but thanks everyone — tripletech, compendium and all those old forums which are lost and forgotten by now.