1. The "no-js" class is invoked to allow Modernizr to run, as it will remove the "no-js" class and replace it with "js". Therefore, your website will render with similar functionality with or without js enabled in the browser.
3. It is available as a zip or a tarball - https://github.com/h5bp/html5-boilerplate/downloads
Point 1: Are you referring to this script?src="//ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script>
Point 2: You can easily copy any of the open source files to your local server, and then point the calls to them. There are certain advantages to pointing to the third-party sources, one of them is that they will always be updated and it eliminates the need for web server administrators to maintain the files. The disadvantage is that you rely on the third party folks to maintain the files and assume they will continue to maintain them.
I hope this helps answer your questions and points.
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