Ceng Shiqiang's video is definitely copyrighted. Although Mr. Ceng Shiqiang has been dead for several years, he must have a family or company to manage the copyright of all his videos, so you can't use them casually. Maybe nobody cares if you take a screenshot or cut a short film, but if you upload it directly to your own website, especially for profit. That's definitely impossible.
Before Mr. Ceng Shiqiang died, all his works were free on Youku. As for the reasons, I think there are about two points. First, knowledge payment had not become a trend at that time. At that time, all works of Youku Culture Channel, including open classes and various tutorials, were free, and Mr. Ceng Shiqiang's works were naturally free. Secondly, with Mr. Ceng Shiqiang's status and position, it is impossible for him to cut off the opportunities for more people to know what he has learned for such a small amount of money. At his age and level, reputation is more important than money.