Youtubedownloader was a KDE GUI for the handy cli tool youtube-dl. It was a fine program in 2007 when KDE 3.5 popular. It has been abandoned for more than a decade and the site where it could be downloaded is no longer online.
What it looked like
youtubedownloader did not offer in terms of functionality, you could paste a YouTube video link into it and download the video. It had an option for transcoding videos to other formats using mencoder (which was popular at the time).