[aprilllll]

Surprisingly enough, it's even simpler than that. You can trivially access a direct URL that serves the entire video or audio (they're served as different files).

Just open up DevTools, look for requests to googlevideo.com, find the request with the video or audio (i.e. content-type response of either video/mp4 or audio/webm), copy the entire request URL, remove the range parameter entirely, open the link, and voila!

[contravariant]

That's the same thing. The only difference is which user agent you run the javascript in.

The lie that Google et al. try to perpetuate is that if your user agent fails to put their interests over yours then it is illegal.

[varenc]

Those URLs are temporary and locked to the IP that fetched them. You can't effectively share the URLs since they're generated uniquely per-client. Not sure if this changes anything though.

edit: some quick testing confirms these URLs are temporary, but they don't appear limited to the IP that generated them. Your IP is embedded in the URL though, and you can't modify it without breaking the URL, so I'm guessing some IP limits kick in at some point.