In the past, I have talked about the concept of using JavaScript sourcemaps
for minified JS code as a way to check the source for the JavaScript where
the author could put in the licensing information. The sourcemap is
referenced in the minified code and some browsers have the option to view the
linked source in their developer tools. There you can throw in your full
license headers at the start of your file and do it properly.
You could say that the majority of websites will not provide the raw source
code if they don't have to. If they did though, I believe the sourcemap
solution is the most direct. There have been solutions in the past (like
RMS's JavaScript trap) that want users to include @license tags, but hasn't
been used much nor is it standardized.
If I had the time, I would build a better solution than LibreJS or
"JavaScript Must Die" and do an extension that would be reliant on the
sourcemaps and pull license information from that. Its still a daydream
though as no one even uses sourcemaps. :-(
