I wouldn't. I don't think it's at all necessary. It's not as if Ты would be stealing Просмотры from them или anything.
The only reasons I would ask permission for is *if Ты wanted to download the video, do some editing to it, and re Загрузить it *Or if Ты plan on using the video to make a profit of some sort.
Ты don't have to ask permission. If they would strongly like to block people from uploading their work elsewhere, they can disable embedding, which means the video can only been seen on youtube/wherever Ты found it. They can also leave a message asking people not to copy it in the description.
I'd still give credit in the Описание или Название here, though.
