Who can use CC0?
Anyone who owns copyright and neighboring and related rights (such as database rights) in a work can use CC0 to give up those rights. But please be careful. CC0 is a one-way street. Once you apply CC0 to your work you can’t change your mind later and re-assert copyright or database rights over the work. In some cases, it’s hard to decide if something qualifies for copyright protection (for example, a database of mostly factual data). Even then, CC0 can be a useful way to assure others that you have committed to surrendering any possible copyright protection you may have. Even though are you not making any warranties of copyright ownership under CC0, keep in mind that you are still responsible to any third parties who may have existing rights in your work when you distribute the work. For example, if your work contains another person’s work made available under a CC Attribution license, you will need to identify that work separately, attribute the author and provide the license. Likewis
