Whenever you want to download a video directly from YouTube, having intent to post it on face book later on, so this is an illegal procedure, without having a copy right license from YouTube. Copyright means to obey all terms and conditions fixed by YouTube when you want to download a video, without having standard YouTube license downloading is totally illegal. You have to grant the broadcasting rules and rights by YouTube, your videos cannot be processed without having a proper license.
But if you just want to share it on face book with your friends then it is legal for you because you are sharing the link to some other spot in its original form not copying, you can do this share with any kind of licenses you have set. You can get the license in some easy steps.
• Click the box ‘License and rights ownership’
• Then pick the ‘Creative Commons – Attribution’ option.
• This step will spot your material as CC BY