How do I know if a YouTube video is available to license?
Generally, the only license that's built in to YouTube is the YouTube terms of service. That license is basically that you have to watch through YouTube. You cannot download, reuse, etc. That leaves you with two options: 1) Link to the video, or 2) use the YouTube embed feature, assuming it's been made available for this video. Outside of that, you'll have to ask the video owner.

However, some content creators licence their YouTube videos under the Creative Commons license (which is only valid if the uploader is the owner, naturally). If a YouTube video is under the Creative Commons or anything other than the standard YouTube licence, then it will say so in the video description. See the following snapshot:



Source

You can also filter YouTube search results to include only Creative Commons uploads.

YouTube also recognizes the "Fair Use" doctrine, and lists their understanding of it and how you may use it with regards to YouTube videos here.