When I open console of Chrome 14 and type...
var input = "# Heading\n\nParagraph";
var output = require( "markdown" ).toHTML( input );
print( output );
var marked = require('marked');
console.log(marked('i am using __markdown__.'));
It's a way to include node.js packages. Luckily, the first package you linked to,
markdown-js, is very smart. It checks whether it is included as a node package, and if not, will set the markdown object to
window.markdown. So all you have to do is include this file in a
<script> tag and you should be able to use the
markdown object from the global scope.