Is it possible to use other javascript libraries?

Edit Subject

You can add in whatever other external JS files you want via dynamic JS loading.

http://ntt.cc/2008/02/10/4-ways-to-dy...

It's really depend on the library you want to use.
The best way to add external JS resources to your app is to use our @include statement like this:

@include "the-url-to-your-js-file"

note: the @include statement must be at the first character of the line and there should not be ';' at the end of the line.

This will add your code (that was fetched from the url) at the beginning of your app code.
As the nature of running inside a sandbox, some of the libraries will have to be slightly modified.

Also, as Mike suggested you can easily load your JS into the regular page/dom (if this is your intention!). You can also use Crossrider's API for this:

appAPI.dom.addRemoteJS("your-js-url");
//OR
appAPI.dom.addInlineJS("your-js-code");