Sometimes, another person can use your copyrighted work and not commit infringement. This happens when the situation falls under fair use.
The U.S. Copyright Office explains fair use is a legal concept allowing the freedom to use copyrighted work without a license under specific circumstances. It is a slightly ambiguous concept, which means a court often has to consider the complete scenario to determine if the use falls under this exception. There are a few loose guidelines you can use to determine if something is fair use.
The use of work should not harm the original value or negatively impact the potential market for the original work.
Nature of use
The goal of fair use is to allow expressive freedom. Therefore, the use should be creative in nature instead of factual.
Type of use
Commercial use generally does not qualify for fair use. Other uses, such as for education or other nonprofit situations, will fall under the doctrine. A use that adds to the original piece or transforms it in some way is another example of fair use.
A line of a song or a small portion of a book used in some other work generally is ok because it is an insignificant amount of the copyrighted work. Using a complete song or book will not satisfy fair use rules. In addition, it matters how much the copyrighted work impacts the overall project. The larger the impact, the less likely fair use applies.
Keep in mind, the court considers all factors when making a determination. Meeting one or a couple of the factors may not be enough to allow fair use.