These sorts of websites let users download audio and video files from YouTube and in their suit, the RIAA claimed that YouTube-mp3.org had around 60 million visitors and tens to hundreds of millions of illegal downloads per month. When the lawsuit was brought forth, RIAA President Cary Sherman said in a statement, "It should not be so easy to engage in this activity in the first place, and no stream ripping site should appear at the top of any search result or app chart."
The website's owner has agreed to pay a settlement, though the details of that haven't been released, and a proposed injunction prohibits anyone associated with the website from having anything to do with a "streamripping" website in the future. The website domain name will also be given to one of the record labels.
The proposed judgement and injunction haven't been approved and ordered by the court yet and the website is still up as of writing, but similar sites and apps are already being taken down. As Mac Rumors reports, ProTube was removed from the App Store last week after multiple requests from Google for it to be taken down.