Which is bad if them notes are not ornaments only. So there should be some fallback. I guess a good approach would be to collect the content from some p.marginnote elements which would be hidden if JS is present and left intact if not. So, like
<a href='#' mnref='gcc'>GCC</a>
...
<p class='marginnote' mnname='gcc'>The GNU Compiler Collection</p>
With JS, they'd become margin notes, whithout it, they'd render as plain footnotes.
It's compatible with the W3C recommended idiom for footnotes[2], is accessible without JavaScript, and you can still use `.marginnote` to provide CSS styling.
Sure, but as the README.md states "adds notes to the margin with the text provided in HTML attributes" it's presumably left up to the user how else they display the data if they want it to be visible for people who disable JS. This library is a progressive enhancement. It's very much the right way to do web dev in my opinion.
It's almost the right way -- somewhat better would be to do what one of the above comments say, to add the notes as footnotes using POSH. Then the javascript can rewrite the footnotes into hide/show marginal notes with the same appearance and user interface as this library.