I think that the standard YouTube terms of service does allow for anyone to interpret the videos there as equivalent to creative commons licensed. Under the YouTube terms of service <https://www.youtube.com/static?template=terms> it is clear that anyone can use videos uploaded to YouTube as long as they do not download the video from YouTube. It seems similar to the CC BY-NC-ND license from Creative Commons. If the YouTube author gives it a CC license, that changes it explicitly to a CC BY license.
- For clarity, you retain all of your ownership rights in your Content. However, by submitting Content to YouTube, you hereby grant YouTube a worldwide, non-exclusive, royalty-free, sublicenseable and transferable license to use, reproduce, distribute, prepare derivative works of, display, and perform the Content in connection with the Service and YouTube's (and its successors' and affiliates') business, including without limitation for promoting and redistributing part or all of the Service (and derivative works thereof) in any media formats and through any media channels. You also hereby grant each user of the Service a non-exclusive license to access your Content through the Service, and to use, reproduce, distribute, display and perform such Content as permitted through the functionality of the Service and under these Terms of Service. The above licenses granted by you in video Content you submit to the Service terminate within a commercially reasonable time after you remove or delete your videos from the Service. You understand and agree, however, that YouTube may retain, but not display, distribute, or perform, server copies of your videos that have been removed or deleted. The above licenses granted by you in user comments you submit are perpetual and irrevocable.
If a YouTube video has a CC license, it can be adapted by other users.
