If resources are freely accessible and are able to be used by anyone they are called "open." These range from resources that are publicly owned or "in the public domain" to resources that are licensed through some creative commons licenses. (Note that some creative commons licenses do not allow for derivative work or commercial use - and so those resources are not open.) A great consequence of a resource being open is that you can use, modify, and make derivative work without contacting the author. Your ability to use and remix is only limited by your imagination and, in some cases, your ability to give clear attribution.
The following is a list of Creative Commons Licenses from least to most restrictive
(See the handy chart below for a visual representation)
Attribution CC BY
This license lets others distribute, remix, adapt, and build upon your work, even commercially, as long as they credit you for the original creation. This is the most accommodating of licenses offered. Recommended for maximum dissemination and use of licensed materials.
Attribution-ShareAlike CC BY-SA
This license lets others remix, adapt, and build upon your work even for commercial purposes, as long as they credit you and license their new creations under the identical terms. This license is often compared to “copyleft” free and open source software licenses. All new works based on yours will carry the same license, so any derivatives will also allow commercial use. This is the license used by Wikipedia, and is recommended for materials that would benefit from incorporating content from Wikipedia and similarly licensed projects.
Attribution-NoDerivs CC BY-ND
This license lets others reuse the work for any purpose, including commercially; however, it cannot be shared with others in adapted form, and credit must be provided to you.
Attribution-NonCommercial CC BY-NC
This license lets others remix, adapt, and build upon your work non-commercially, and although their new works must also acknowledge you and be non-commercial, they don’t have to license their derivative works on the same terms.
Attribution-NonCommercial-ShareAlike CC BY-NC-SA
This license lets others remix, adapt, and build upon your work non-commercially, as long as they credit you and license their new creations under the identical terms.
Attribution-NonCommercial-NoDerivs CC BY-NC-ND
This license is the most restrictive of our six main licenses, only allowing others to download your works and share them with others as long as they credit you, but they can’t change them in any way or use them commercially.
The chart below shows which CC-licensed material can be remixed. To use the chart, find a license on the left column and on the top right row. If there is a check mark in the box where that row and column intersect, then the works can be remixed. If there is an “X” in the box, then the works may not be remixed unless an exception or limitation applies.