You are not allowed to download videos from any supported host for commercial use. You are not allowed to download copyrighted videos. It is for personal use ONLY! For backup of your own videos or if you want to create your own video you might use parts of other videos under the fair use law - 17 U.S. Code Paragraph 107 - Limitations on exclusive rights: Fair use -
Yes, Fooja can encode a youtube video into mp3 files. Thats works for youtube videos only. A special codec is needed. If fooja doesn't find it on your pc, you can approve the download of the codec.
You can find the codec here when you allowed Fooja to download: /Documents/ffmpeg
Make sure that all videos are public. Specially for facebook, you have to watch the video without log-in to your account. Make sure that you can watch the Youtube video in your country. Some videos might be blocked. Those videos you can't download.
After payment was successfull, you get access to http://customer.jvzoo.com (if you paid via paypal). Please login and access your purchase. That will lead you to your license key.
Beside that you get an email with your license key.