mode-funcdown.js is for Ace Editor.
funcdown.sublime-syntax is for Sublime Text Editor.
Place/save the file in Your ace/ directory where main ace.js is and other mode-*.js files are.
Place/save the file into Your ~/.config/sublime-text/Packages/User directory.
Funcdown is "c-function syntax alike" markup language generator.
Go to Funcdown Playground to see it in action.