Did you try to open the website on your computer?
It should work even when you are offline, after you have entered the first time.
If that is enough for you, there is no need to download anything. Its designed to work like that.
Please, can you test that for me? Just try to open 
javatari.org, even when offline. It should work.
Or, if you prefer, you can just right click -> Save As and save the HTML page on your computer... It is a single file. It will also work this way!
Please let me know if you succeed!
Paulo