jQuery Forum

https://github.com/jquery/jquery/tree/master/src 

you will need core, support, callbacks, deferreds, ajax, event, data, and possibly others.

-- Kevin

It appears that the logic that I required of jQuery AJAX (the "script" data type) is easily implemented by dynamically creating a "script" element and assigning relevant event handlers for callback.

For future any readers, the following source helped me to reach this conclusion:

https://github.com/jquery/jquery/blob/master/src/ajax/script.js

And the following explains how this works:

http://www.ejeliot.com/blog/109

Best wishes