Open Educational Resources (OER) are teaching and learning materials that you may freely use and reuse at no cost. Unlike fixed, copyrighted resources, OER have been authored or created by an individual or organization that chooses to retain few, if any, ownership rights. In some cases, that means you can download a resource and share it with colleagues and students. In other cases, you may be able to download a resource, edit it in some way, and then re-post it as a remixed work.
OER often have a Creative Commons or GNU license to let you know how the material may be used, reused, adapted, and shared.
All Creative Commons licenses have many important features in common. Every license helps creators retain copyright while allowing others to copy, distribute, and make some uses of their work — at least non-commercially.
The GNU General Public License is a free license for software and other kinds of works that allows an individual to use, adapt and share software.