I would like to know if it is possible to download and include the jsapi library, but not hosted by google.com, hosted on my local machine. Because it's possible that my project can not have access to the Web.
You can't.
You can download jsapi.js and save it in your local machine, but it will still refer to the on-line version on google.com. You can see it by opening the jsapi.js code.
See this Google developers article for more.
Can I use charts offline?
No; your computer must have live access to http://www.google.com/jsapi in order to use charts. This is because the visualization libraries that your page requires are loaded dynamically before you use them. The code for loading the appropriate library is part of the included jsapi script, and is called when you invoke the google.load() method. Our terms of service do not allow you to download the google.load or google.visualization code to use offline.
Can I download and host the chart code locally, or on an intranet?
Sorry; our terms of service do not allow you to download and save or host the google.load or google.visualization code.