How do you reference a js library in a code page?

NO. Most libraries you find on a CDN will have built in code that will detect how they should be loaded. Since QuickBase used requirejs to load AMD modules most libraries from a CDN will assume they should load as AMD modules not as globals. Snowstorm is an oldschool library and loads through a global but loading through a global is becoming more unpopular over time.

For example d3 version 4 from a CDN would be loaded into a QuickBase page using requirejs:

require.config({
  paths: {
    "d3": "https://cdnjs.cloudflare.com/ajax/libs/d3/4.9.1/d3";
  }
});
require(['d3'], function(d3) {
  console.dir(d3);
});

In contrast d3 version 3 loads through a global.

At times I have been giving advise to modify libraries and remove loading logic at the head of the file because most users of QuickBase don't have the experience to wade through the proper was to load AMD modules.

It can be very confusing. Most of this nonsense will go away once JavaScript modules are widely supported:

http://caniuse.com/#feat=es6-module

Here is a little trick you can use to detect what libraries have been configured to load as AMD modules in QuickBase:

console.dir(requirejs.s.contexts._.config );

Note in the above console screenshot d3 was manually required so it shows up in requirejs's internal context in addition to all the other modules QuickBase has configured to load.