the html is fairly basic boilerplate for a full screen map, but the JavaScript file includes the data as well as the code to display it, in production we'd probably want to serve that as jsonp. This can be entirely self hosted internally, except the tiles which are hosted by mapquest in this example and we'd have to render our own tiles if we wanted to host them.
Modified http://cdn.leafletjs.com/leaflet-0.3.1/leaflet.js to a secure url
Modified http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js to a secure url
https://cdn.leafletjs.com/leaflet-0.3.1/leaflet.js
https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js