The demo you are trying to implement has changed quite a bit since jsPlumb 1.3.3. If you want the version from 1.3.3, you can see the old code in the repo:
- https://github.com/sporritt/jsPlumb/blob/04013d793cae682ca7b361b5550fb8583b028bfe/demo/jquery/chartDemo.html
- https://github.com/sporritt/jsPlumb/blob/04013d793cae682ca7b361b5550fb8583b028bfe/demo/js/1.3.3/chartDemo.js
Implementing that demo with 1.3.3 should work.
If you want to upgrade to 1.5.5, you can pick one of the jQuery-compatible distributions from the jsPlumb dist/js folder.