It's a javascript file. I don't use front page, so I have no idea where it came from or what permissions you have. But in general, websites allow end users to download .js files since they do stuff on webpages.
JS = JavaScript. JavaScript is client-side code, so that means the user has to have permissions for it. Generally it's best to include JS as an external file (".js" just like it's better to use CSS as an external ".css").