answer:1) yes, you have to ask permission for all but the smallest snippets – like a second or two 2) if you just do it, the publisher can send Youtube a message and Youtube will take your video down. You can fight the takedown, but it’s unlikely you will win. Note that copyright owners have various automated systems that scan through all of Youtube, so there’s a good chance you would be found. 3) your best bet is to find some websites (there are a few such as this this is but one example ) that let you use their stuff.