Can public domain content be licensed?
<p>I was skimming the &quot;Stack Exchange Network Terms of Service&quot; until I came across:</p>
<blockquote>
<p>Profile Content that is available via the Stack Exchange API (&quot;API Profile Content&quot;) is perpetually and irrevocably licensed to Stack Exchange and its Subscribers under the Creative Commons Attribution Share Alike license</p>
<p>Profile Content that is NOT available via the Stack Exchange API (&quot;Personal Profile Content&quot;) cannot be used for any commercial purpose, individually or in aggregate, or be republished without the explicit consent of the author of such Personal Profile Content or the explicit consent of Stack Exchange.</p>
</blockquote>
<p>The thing is that I found my profile picture I use in StackExchange.com websites online from a website claiming it is in public domain. Now I am wondering if I have unintentionally licensed this public domain image to StackExchange Inc. or myself? In other words does the image on the source website stay in the public domain?</p>
<p>Note: I have cropped the image to use in my profile.</p>

<p>My answer assumes that the photo you found is in fact in the public domain. See <a href="http://fairuse.stanford.edu/overview/public-domain/welcome/" rel="nofollow" title="here">here</a> for how works can enter the public domain (in your case, you're hoping that it was "dedicated" by the photographer, and not otherwise assigned to some third party who is not the photographer, e.g., his employer).</p>

<p>Assuming it's in the public domain, what this means is that nobody has any of the exclusive rights to the work anymore (see <a href="https://www.law.cornell.edu/uscode/text/17/106" rel="nofollow">17 U.S.C. 106</a>). </p>

<p>Now, a bit of property law. You can imagine the list of exclusive rights listed above as a handful of post it notes. One says, "to reproduce the copyrighted work..." Another says "the right . . . to display the copyrighted work publicly." Someone who owns all of these exclusive rights can do anything he wants with them. He can give one of the post-it notes away permanently (assignment) to another person, or he can give it away temporarily (usually, a license). He can give away just one, or all at the same time.</p>

<p>The terms of this website are effectively requiring you to let SE borrow, forever, the post-it note that says "publicly display" <strong>so that they are not violating your exclusive right of public display</strong>.</p>

<p>However, this assumes you even own that exclusive right (post-it note). Something in the public domain no longer has any rights (post-its). No exclusive rights exist at all with respect to such a public domain work <em>in copyright</em>.*</p>

<p>Therefore, since you do not possess any copyright rights with respect to a public domain work, you have nothing to give to SE, and so you have not given anything to SE.</p>

<p>The answers to your questions therefore are "no you have not licensed anything" and "yes it stays in the public domain".</p>

<ul>
<li>Other rights can apply to images, such as trademark. If the image is of a person, there is also the right of publicity. See <a href="http://www.copylaw.com/new_articles/PublicDomain.html" rel="nofollow">here</a> for more info.</li>
</ul>

copyright licensing public-domain