Export `foo` to `window`.

gistfile1.js

(function (global) {
    'use strict';

    var foo = function () {
        return this;
    };

    if (global.namespace === undefined) {
        global.namespace = {};
    }
    global.namespace.foo = foo;
}(this)); // this === window in global context

// Now you can get foo from your namespace
window.namespace.foo();