What's the reason to include scripts with two different calls?

Question

I use HTML5 boilerplate and jQuery is declared twice in the HTML page like this:

Answer 1

Loading jQuery from the Google CDN can be much faster than loading it from your local server and it can be cached so the user might already have a cached copy of it from another website.

The check is make sure that it got loaded, otherwise if it failed, load it from the local server.