If you're trying to run a HTML page as Groovy script then you're doing something horribly wrong... Just stick with the default fn:amc if you don't know what you're doing.
I recently installed filebot on Mac OS Darwin, via some convoluted process and it's on... but the ~/Documents/filebot/Groovy Scripts/ folder had three groovy's in there, but they were HTML text versions of the actual groovy script... and using Mac OS X TextEdit.app copying the "raw" code from Github produced the same result, it wouldn't convert the result of the Github table to just the text within.
I installed "Sublime Text 2".app to handle my Groovy editing. No more issues with HTML formatting permeating into the raw code.