The LICENSE, LICENSE.md, or
LICENSE.txt file is often used in a repository to indicate
how the contents of the repo may be used by others.
People who incorporate General Public License (GPL’d) software into
their own software must make their software also open under the GPL
license; most other open licenses do not require this.
The Creative Commons family of licenses allow people to mix and
match requirements and restrictions on attribution, creation of
derivative works, further sharing, and commercialization.
People who are not lawyers should not try to write licenses from
scratch.