The Library of Congress and Public Domain.
If a work, such as a book or a photo, is in the public domain, that means that no one holds the copyright on it. You can do whatever you want with it. Download it, alter it, sell it, use it in an ad, whatever, it's up to you. The only thing you can't do with it is claim copyright on it, because it's not copyrightable; that's the nature of PD. PD images are the freest of the free, and I love them.
There are only three ways that an image could be in the public domain. (These rules work for other types of files too, such as documents or movies.)
- If an image is old enough, its copyright may have expired, putting it in the PD. But it has to be pretty old. Assuming the picture was made in the USA, its only in the PD if it was created or first published before January 1, 1923. So this photo of the Deleware flood is PD, since it was taken in 1913, but this photo of the result of a hurricane is copyrighted, and if you use it, the copyright holder can sue you.
- If an image was made by an organization that cannot legally claim copyright, then the image is automatically in the PD. This is pretty much limited to the US Federal Government, or the California State Government. So this official Whitehouse photo is in the public domain, but this one, taken by the Associated Press, is not.
- If the copyright owner of the image expressly releases it in to the public domain, then it's in the PD. If you want to release something of your into the PD, simply state on the document somewhere that you release it into the PD, and link to the Creative Commons public domain license. It's pretty easy. All the text on this site, for instance, is released into the public domain.
There are some images, however, where someone still owns the copyright, but the terms for reuse are pretty generous. I'll describe some of these so-called "free licenses" in a later post. For now, have fun digging around the Library of Congress for diamonds in the rough.
All information on this site is correct to the best I can determine; however, nothing on this page should be construed as legal advice, and I cannot be liable for any damages if this information is inadvertantly incorrect.