In order to compile jasshelper.grm into jasshelper.cgt (if you modify) you need the Gold Parser Builder http://www.devincook.com/goldparser/ 
I used version 3.4.4 
Gold Parser Versions >= 5.0.0 do NOT work with jasshelper, you need older ones.

When you compile the grammar you need to regenerate symbols:
Tools -> Create Skeleton Program -> Delphi (Constants Only)
Than you need to copy generated symbols into jasshelpersymbols.pas (do not just overwrite this file, do manual copy)