I have added a ; at the end of said regex and now have this: ^.+ytplayer\.config\s*=\s*(\{.*?};)

For this particular use-case the above regex extracts the JSON. Although JSON's decode_prefix() will ignore any trailing non-JSON (e.g. the Javascript I mentioned) content. Now, regarding the problem of unquoted keys and values. There is a allow_barekey() option to the JSON parser which will allow keys not to be quoted.

And you need to deal with the remaining problem of unquoted values. Unquoted values may be indicative of a much bigger problem: that values in the "JSON" (which is actually a Javascript hash) are function calls or other hash values, variables etc.! For example, this is the line that _get_args() looks for:

if(createPlayer){
  if(window.ytplayer.bootstrapPlayerResponse){
    window.ytplayer.config={args:{raw_player_response:window.ytplayer.
+bootstrapPlayerResponse}};        
    ...
[download]

There is a reason why it is unquoted I think ...

So, yes the scrapper looks outdated (though very recently updated) and you are better off using something else.

bw, bliako