Instead of “all rights reserved” some people opt for “no rights reserved.” But can an author really put his or her work in the public domain? And if so, how? Is there such a thing as a public domain license? Let's see.
Not everyone wants to exercise their exclusive copyright rights. Some people dedicate their works to the public domain because they want people to use them with no strings attached. That's a wonderful and generous thing to do, but if you're planning to use any such work, be sure that's what the author really intends.
Since copyright is automatic, if a work's author wants the work to be in the public domain he or she must do something to put it there. Generally, the author just has to make clear her intention. Writing is best, for obvious reasons. (In case of disagreement, you've got something besides “he said, she said” to fall back on.) Okay, great ... but what kind of writing?
Nothing in the US copyright statute specifies how to abandon one's copyright. As I just said, copyright is automatic—as soon as an original and minimally creative work is fixed in tangible form, it's protected by copyright. Once copyright has attached to a work, some scholars argue it's not possible for an author to abandon it, while others say it's merely difficult.
So let's get an answer straight from the copyright horse's mouth, shall we? Here's how the Copyright Office responded to me in a private email:
There is no specific provision in the copyright law for disclaiming rights in copyrighted works, and of course, no obligation to do so. However, the Copyright Office will record a statement of your intention to relinquish rights in our official records because the document pertains to a copyright within the meaning of the statute. A statement of abandonment should identify the works involved by title and/or registration number. The office does not provide forms for this purpose.
The legal effect of recording a statement of abandonment is not clear. Moreover, its acceptance for recordation in this office should not be construed as approval of the legal sufficiency of its content or its effect on the status or ownership of any copyright.
Well that certainly cleared things up, didn't it? So, although you might read that such-and-such work has a public domain license (especially in the realm of software), and you might read that public domain declarations are, in effect, irrevocable licenses granting free usage to everyone ... there is no consensus on the legal effect of such declarations. FYI.
So where does that leave you (and me)?
Know what to look for.
What you want to see, basically, is unequivocal language acknowledging that the author is giving up all rights in the work ... and allowing you (and everyone else) to do whatever you want with it. It's best if the public domain dedication is in writing and the author's intention clearly expressed. If it isn't, you'd better verify.
If the author uses language that indicates he or she intends to control the work in any way whatsoever ... it's not a public domain dedication. Putting a work into the public domain means giving up all control over how the work is used. It's a giving up of all rights to the work, forever.
This public domain dedication from Creative Commons is a good example of the kind of language you'd want to see. You'll note that the document is not a license—it's a "copyright-only dedication."
Patent, trademark, and publicity or privacy rights arent affected. Also, please note that the work may not be free of copyright restrictions in all jurisdictions because copyright terms vary from country to country. (The legal language behind this decication is here.)
Note: As far as I know, the Creative Commons public domain dedication has not yet been tested in court.
If it's clear that the author has dedicated his or her work to the public domain, great! If you're not sure, ask.
Now ... since we're on the topic of language and clear intentions, let's talk about contract language, and the way license agreements are being used (more and more) to restrict what you may do with public domain work.