WEBCAM: "open /dev/video0: Permission denied"

Нашел здесь.  

I solved the problem. You must give to the user (you) permission for use video devices. Go to System > Administration > Users and Groups. Unlock and select your username. In user privileges, you must enable the line "Capture video from TV or webcams, and use 3d acceleration", log off and log in.

I hope that help you. Greetings,