A script that runs in its own anonymous iframe has a lower impact on the host page since HTTP requests happen in parallel, and global variables / functions do not affect the host page.

In the section
"When does the script interact with the DOM (choose all that apply)"

Probably needs more documentation to specify if this includes

• Attaching event handlers
• Reading document.cookie
• Writing document.cookie
• Reading document.domain
• Writing document.domain
• Creating/removing DOM nodes

I was trying to fill the questions for my script but there are some that do not apply. Is ot right to answer the A for them?

In this section: "If the component adds event listeners to DOM elements, does it remove them when they're no longer required?"

It isn't clear whether this applies to event handlers for window.onload, DOMContentLoaded, unload, onbeforeunload, pageshow, pagehide, and other events that only fire once.

Scripts that can be loaded asynchronously but still block the onload event should receive a B rating. Only scripts that can either be loaded in/after the onload event or scripts that use the advanced Iframe Loader Technique should get an A rating.

The loader is described here: http://calendar.perfplanet.com/2012/the-non-blocking-script-loader-pattern/

Apart from the MTTR section, there should also be a question about whether a slow loading script results in the page blocking (ie, onload not firing) for a long time.

Most asynchronous loading scripts will still block onload, while scripts using the iframe loader technique or loaded after onload will not block onload.

First off. I really like your idea here! But instead of answering such a long form about the code; perhaps it should be turned into a service where you simply point to a gist for dynamic analyzation. If it was that easy to use, it would probably become mainstream. When it's finally mainstream, package-managers etc could use the rating for sorting.