Unfortunately MathJax is a bit large and nontrivial to host yourself. And it recently switched to being hosted on cloudfare instead of mathjax.org.

I struggled with this choice myself and so far, decided to do the same as the author with a noscript tag to explain to the reader why I'm loading cloudfare code.

No it's not, but most people don't think about it. Mathjax used to have their own CDN by the way. Not sure why they pulled it.