IIRC the old yt-dlp was removed at one point for exactly that.

Google's already tried taking down Invidious. If they could use the DMCA for it, I believe they would. Notable, Invidious is still up, and there were fun articles from the response

https://www.vice.com/en/article/youtube-tells-open-source-pr...

it'll just cause a lot more people to become aware of it and cause mirrors to pop up everywhere.

Weirdly enough, Google's never actually made a public statement that YouTube "has DRM". If they did, it would immediately give Kevin McLeod the biggest copyleft trolling opportunity in history, because all Creative Commons licenses specifically forbid using DRM on the resulting work.

The only reason why we even know YouTube "has DRM" is because third parties have been able to plausibly allege DMCA 1201 circumvention claims against yt-dlp regarding a nebulously named "rolling cipher". These are not actual court findings of fact, just that you can say this in a legal filing and not immediately get your case thrown out on summary judgment. Which is a really low bar. Whether or not the rolling cipher actually qualifies as DRM is still an open question.

The way DMCA 1201 is written, basically anything intended to function as copy protection is considered DRM under the law. Like, those really annoying no-right-click scripts people used to put on sites probably could be argued to be DRM under DMCA 1201. However, in this case, there's a disconnect between the people offering the DRM (who don't actually claim it's DRM) and the people using it as DRM.