[couchand]

It might be useful to automatically cross reference to a source like GitHub or NPM. Code could very well have licensing information at the source, but not serve it to web clients. Just the name of the library would be enough to get a lot of these.

[davexunit]

The name is not nearly enough. I could serve a jquery-1.11.1.js file that has my own proprietary modifications. A checksum could fix this. However, what about when minified JavaScript is served, as is often the case? What source code corresponds exactly to the "binary" (minified source)? People use different minifiers/uglifiers with different settings. And then there's the issue of minifying all of your source files and then concatenating them into a single file. It's a tough problem.