It's very possible to have a TOS violation but not a copyright violation if you're the copyright owner of the video being downloaded. Owning the copyright mean

It's very possible to have a TOS violation but not a copyright violation if you're the copyright owner of the video being downloaded. Owning the copyright means you don't violate the copyright in making a copy, but that doesn't mean you get to make that copy through any means; you still have to use legal means, and for a website, that means methods that are acceptable under the TOS of that website.