All open resources you find are not OER. Just because something is open and available to you does not mean that it is available to revise. As discussed in the "What is OER?" page of this guide, we typically refer to OER as having the 5 R's: the ability to Retain, Reuse, Revise, Remix and Redistribute the content at no cost.
Most OER are licensed under Creative Commons licenses, allowing content creators to authorize permission to use their work in specific ways while still retaining copyright protection. Every Creative Commons license designation requires users to give attribution to the creator of the work. The only exception is if the resource is found within the Public Domain (the copyright has expired or was forfeited); items within the Public Domain may be revised without any restrictions and do not explicitly require attribution.
There are a variety of Creative Commons licenses available; please refer to their guidelines and requirements before modifying the licensed content. The most up to date licenses are version 4. Version 3 licenses will still work for OER; version 2 licenses might have outdated standards.
Note: You may see CC licenses of CC BY-ND or CC BY-ND-NC but these licenses do not allow adaptations or derivatives and are therefore not suitable for OER.
Creative Commons licenses require you to accurately attribute to your source.
The Creative Commons wiki includes a detailed guide on Recommended Practices for Attribution.
If you are interested in licensing some of your new material or if you are required to license remixed material under one of the CC SA licenses, the Creative Commons License Chooser can guide you though the process. You will then need to copy the HTML code and insert it into your website on the pages you wish to license under Creative Commons. For documents, insert a statement with the license and a link to the appropriate license. Creative Commons has a wiki for Marking Your Work With a CC License and also has an extensive Frequently Asked Questions page if you are interested in learning more.