yt-dlp appears reasonably safe (hence the >7K stars on Github). It is a fork of
youtube-dlc (now also a dead project) which was a fork of
As you can probably tell, it is much more active in terms of development and has many extra features such as better extractors and other options. In most cases, minimal to no changes are required when transitioning from one to the other. I transitioned a few weeks ago with no problems whatsoever.
As for what happened to the original, I'm not sure anyone has any idea, you could try opening an issue on Github asking about it, but don't expect any responses that aren't from the developers themselves to be reliable.
In general, I think
yt-dlp is better anyway - they process pull requests and respond to issues a lot faster too. I don't see any drawbacks in using it for development over
youtube-dl, except that because it constantly has new commits, it might be considered more unstable (but
youtube-dl is currently inactive anyway, what choice do you have?).