"Historically, copyright has often been regarding as an either/or choice. Either you reserve all rights to your content (ie, copyright 2004 Andy Carvin, All Rights Reserved), which means no one can really do anything with your work until they've gotten permission from you. Or, you make your content available to everyone with no strings attached, basically giving it away -- in other words, putting it in the public domain.

The Creative Commons initiative has come up with a set of copyright licenses that allow you to say to the world, "Some rights reserved." In other words, you can use their licenses to encourage use of your work in certain circumstances, while restricting it in others. For example, let's say I've written an article about the digital divide in Boston. I want people to read it and distribute it, but I don't want them making money off my hard work. Creative Commons allows me to license my article so that it may be distributed for noncommercial purposes without seeking my direct permission, but anyone who wishes to use it for commercial purposes would have to check with me first. Another example: I've just created a tutorial on ICT literacy that I plan to sell in the US and Britain, but I don't want to charge users from developing countries. Creative Commons can help you do that as well.

How Does it Work?

Essentially, Creative Commons is a way of designing a personalized copyright license for your work, whether it's an article, a blog, a photograph, even music or video. There are seven different licenses available, each of which I'll outline below.

What are the Rules of Creative Commons Licenses?

Each of the seven Creative Commons licenses is a combination of different rules you choose to apply to your content. Here's a description of these rules.

Attribution. When you select a license that includes attribution, it means that anyone who wishes to copy, distribute or display your work must give you credit for it. This element is now standard in any licenses generated through the Creative Commons website, and on social media sharing websites. For example, all Flickr.com photographs which are given a Creative Commons license have attribution as standard.

Non-commercial Use. If you want your work to be used by others for noncommercial purposes only, this is an important feature. Anyone who wishes to use your work for commercial purposes would have to seek your permission. If you don't select this feature, anyone will be able to use your work, commercially or otherwise.

No Derivative Works. If you select this setting, no one else will be able to edit your work. They'll have to use it as-is. If you skip this setting, you give permission for people to edit and repurpose your work.

Share Alike. This allows people to make derivative works of your content, but only under the condition that they apply the same Creative Commons license to their version when they publish it. That way, the benefits of the license get passed along from one generation of content to the next.

What Types of Licenses Are there?

When you choose a Creative Commons license, it will contain one or more of these rules, depending on your personal preferences. There are currently seven licenses available:

[Edit: Creative commons version 1 had 11 valid variations, but because most people chose the attribution element they made this standard in v.2, thus reducing the valid variations to six]

Attribution License. Users must give you credit when disseminating your content.

Attribution-NoDerivs License. This combines two rules: attribution and no derivatives. In other words, anyone may use and distribute your work as long as they give you credit and don't make edits to it.

Attribution-NonCommercial License. Users must give you credit when distributing your content and may only use it for non-commercial purposes.

Attribution-NonCommercial-NoDerivs License. The same as the previous license, but with the additional rule that users may not make derivative versions of your content -- i.e., they can't edit it.

Attribution-NonCommercial-ShareAlike License. Users may distribute and edit your work as long as you are given credit and it's for non-commercial purposes and if they pass along the same Creative Commons license to their users in turn.

Attribution-ShareAlike License. Similar to the previous license, except that it's okay for others to use your work for commercial purposes.

Developing Nations License. The newest type of Creative Commons license, it grants users in developing countries greater freedom to use your work than users in developed countries. It's basically an Attribution-ShareAlike license: users in developing nations may distribute and edit your content as long as they give you credit and pass along the same Creative Commons rules to their users. Meanwhile, people from developed countries must seek your permission before they can distribute or edit your work."

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Note: There is also a Public Domain 'license' (a dedication actually) - see the 'Other Licenses' section here - http://creativecommons.org/about/licenses/meet-the-licenses

So, almost all current Creative Commons licensed images (for example) will require at least attribution "in the manner specified by the author or licensor". Presumably you thus have to scour the source for information on how the author wants to be attributed, or even try to contact the author and ask them? You still can find material licensed with the older CC variations.

Basically, the only time you can simply take something and use it freely with no rules or restrictions (especially if the use is commercial) is if it is clearly marked as public domain (that's a 'PD' in a circle if done via Creative Commons).

- text slightly adapted but mainly lifted from http://www.digitaldivide.net/articles/view.php?ArticleID=70
and reusable under the same license terms, natch!

This chap has a serious issue with CC...
http://www.pcmag.com/article2/0,1895,1838244,00.asp

Here's a nice cartoon explaining the theory...
http://creativecommons.org/about/licenses/comics1
See page 4 showing the 11 valid variations possible with CC v.1.

Here's Wikipedia's entry for CC

If you break the license terms on a CC'd image (etc) you could be sued for damages. See http://technology.guardian.co.uk/weekly/story/0,,2002905,00.html for how much the big image vendors claim for copyright infringement.

Public Domain images

Public domain images are copyright free.
There is a list of public domain image sources at http://en.wikipedia.org/wiki/Wikipedia:Public_domain_image_resources
As they state "The presence of a resource on this list does not guarantee that all or any of the images in it are in the public domain. You are still responsible for checking the copyright status of images".