Question about youtube to mp3 firefox add on downloaders and audio recorders?

Are firefox add ons like video2mp3 and youtube mp3 that converts youtube videos to mp3s as well as audio recorders like audacity legal? Cuz i mean they r firefox add ons and aren't the people uploading songs on youtube doing it illegally in the 1st place so is this illegal n can u get caught for it? Im confused! Please help! Oh also what about Orbit downloader? These are just some of the programs i have heard about that some of my friends use