But that's not what really nails it. You agreed to YouTube's usage when you went there.
2. https://www.youtube.com/static?template=terms and down the page writes:
"You shall not download any Content unless you see a “download” or similar link displayed by YouTube on the Service for that Content. You shall not copy, reproduce, distribute, transmit, broadcast, display, sell, license, or otherwise exploit any Content for any other purposes without the prior written consent of YouTube or the respective licensors of the Content. YouTube and its licensors reserve all rights not expressly granted in and to the Service and the Content."
So that's 2 strikes and let's just write no.
Is VideoZonk a legit application??