I'm a freelance writer and decided to write a book basically by transcribing someone's else talks in a different language.
A person has 50 videos where he talks about certain subjects. Theses videos are free of use and don't have any copyright, people are encouraged to share. Basically, someone recorded his voice during his talks and with his consent. Then he uploaded it on YT and now I decided to transcribe it in my native language. I'm planning to publish the book and maybe offer for sale.
Do I still need to contact the author of the video or the speaker and ask for the approval to use his speech as the subject of my book? Or since it will be in a different language the product's form will be contributed solely to me as an author? Maybe pointing him as a reference but how do you reference a youtube video?