"It would be interesting if we could make a youtube-dl that dynamically fetched the latest working version ..."

I think a better strategy would be to separate the youtube-dl core "engine" from the set of rules/exceptions/offsets that it uses to iterate and download the media.

So the core youtube-dl could not download anything (or, perhaps, only a simple file at a static URL) and you would add a set of rules, or specs, that give it the ability to download from youtube or vimeo or whatever.

Then you would not worry about blocking youtube-dl or having it barred from github, etc. and all of the "rules" could be simply shared, or published, as simple text via pastebin or email or whatever.