Answer: The key distinguishing characteristic of OER is its intellectual property license and the freedoms the license grants to others to share and adapt it. If a lesson plan or activity is not clearly tagged or marked as being in the public domain or having an open license, it is not OER. It’s that simple. While custom copyright licenses can be developed to facilitate the development and use of OER, often it can be easier to apply free-to-use standardized licenses developed specifically for that purpose, such as those developed by Creative Commons or – for software – those approved by the Open Source Initiative.