The original script had an error, the converter is unable to fix dumb scripters' mistakes. I don't blame them, though, iBot doesn't have a proper Lua debugger:
CREATURES = CREATURES or {
"Giant Spider",
"Acid Blob",
"Ice Golem",
"Water Elemental",
,
},
See that comma over there, without a creature name? That wouldn't let the script run correctly, even on iBot. Just remove that extra comma, and then click on Convert From iBot (on the scripter window). And then you are good to go.