Q. Do I have to change and contribute to materials I find online, or can I use them as they are?
Under certain Creative Commons Licenses, you are free to remix as you choose. However, it is not required! Many OER can be used exactly as you find them. If you have created your own OER, you may choose to apply any number of restrictions under Creative Commons.
To learn more about Creative Commons and the different types of licenses that are available, see their website at creativecommons.org.