Is there an app for the iPhone that lets you download videos to watch with no Wi-Fi?

I have tried almost all the free apps out there but they all say that downloading from youtube is copyrighted. I don't need to save it to my camera roll; I just need it so I can go back and watch it when I'm on vacation with no Wi-Fi.

There are lots of programs that you can use on your computer that will download youtube videos. Use that then put it on your iPhone.