Works In The Public Domain
Works that are in the public domain include generic information such as work donated by authors directly into the public domain, document titles and names, facts, numbers and even words that you create, unless trademark protected to represent your brand are part of the public domain.
Other material that ends up in the public domain includes content or documents that were once copyright protected but the author failed to update the copyright.
You can also take existing public domain, add your own spin on it, including modifying content, adding in images, translating the document into a new language, or adding in new, original content and copyright it yourself so that it belongs to you, however the portion of your content that was originally pulled from the public domain remains in the public domain, where others can use it in the same way that you did. All of the material that you personally added however, is protected and owned by you.
This is called “derivative work” and is a common method of recreating existing public domain so that it’s a fresh product that you can claim (and protect) as your own.
You can also sell image prints that are taken from the public domain, by reprinting them into photos, paintings, posters, postcards and even wall art. There are many successful companies doing this online, as well as selling on eBay and even Amazon.
One great source for public domain imagery, is by browsing through the Library of Congress, available at:
http://www.loc.gov/library/libarch-digital.html
Other sources for images found within the public domain include:
http://digitalgallery.nypl.org/nypldigital/index.cfm , which hosts an incredible image library showcasing over 1 million public domain images.
One thing to keep in mind when it comes to using public domain is that there are two ways to get it, directly and indirectly.
For example, if you visit a website such as the Digital Gallery you will notice that they apply license restrictions to the images they host, even though they are featured within the public domain.
They can do this simply because they are the ones distributing it, meaning that if you download it from them, you are required to comply with their restrictions.
However, if you dig into the public domain yourself, find the exact same images without ever having to follow any restrictions or licensing rights.
This means, that while there are many sources for exploring public domain content, if you ever encounter a website that requires you agree to their terms of licensing, try going directly to the public domain databases yourself, to find the material you are looking for