The MIT-0 license begins with a copyright statement.

MIT No Attribution


Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so.

The 0BSD license does as well. But both of these are discussed on Wikipedia's Public-domain-equivalent license page.

On the other hand, the Unlicense does not. The CC0 license is very long as it tries to cover both true public domain grants, as well as giving everything away in countries where the law doesn't actually allow you to not copyright something.

Should the MIT-0 and 0BSD be considered public domain declarations? Or do works released under them remain under copyright, just with the author giving them away with no restrictions? Or are those two things basically legally identical in most countries?

  • 4
    The licenses explicitly say "Copyright" in them. Why would you think that's not a claim of copyright, which, by definition, precludes the public domain?
    – jwodder
    Commented May 4 at 15:14
  • 1
    @jwodder I think the OP is really trying to understand whether these two licenses are in effect identical to the public domain. I don't think OP means to ask if they are technically the same.
    – xuhdev
    Commented May 4 at 20:31
  • I added a link to Wikipedia's Public-domain-equivalent license. I'm asking because it seems a little odd for MIT-0 and 0BSD to be considered public domain when they start with a copyright declaration. Commented May 5 at 2:18

3 Answers 3


The distinguishing characteristic of public domain works is that no intellectual property rights apply to them. This may be because of the nature of the work or of its creator, because the owner of the rights renounced them, because of the age of the work, or for some other reason. There are jurisdictions that do not recognize some of those avenues into the public domain, but that does not necessarily mean that they don't recognize the public domain at all.

Should the MIT-0 and 0BSD be considered public domain declarations?

No. These licenses literally assert copyright. They grant unrestricted rights to all recipients, but if they were effective public domain declarations then their primary effect would be that there wouldn't be any rights to grant in the first place.

Or do works released under them remain under copyright, just with the author giving them away with no restrictions?

Yes. These licenses assert copyright. They rely on copyright to have any effect. They nowhere say anything about relinquishing ownership of copyright, disclaiming rights, or the like. They grant broad rights to others, which is something different.

Or are those two things basically legally identical in most countries?

In a country that does not recognize copyright relinquishment, a plain public-domain dedication (probably) has no effect at all. That is legally very different from the effect of a permissive license, which is exactly the issue that CC0 attempts to address. In a country that does recognize copyright relinquishment, the effect of a supremely permissive license such as MIT-0 is similar to, but not the same as, an effective public domain declaration. The differences revolve around the continuing existence of copyrights. For example,

  • licensees can exercise the broad rights granted to them, but they do not own the rights, and therefore cannot themselves dedicate the work to the public domain.

  • Derivatives of a permissively-licensed work are, in fact, derivatives, which has copyright implications that differ from those for derivatives of public domain works. The creators of such derivatives can still do most of the things they might want to do with their works on account of the original's permissive licensing, but not quite everything.

  • The owner of a permissively licensed work can distribute it under a different license, either concurrently or at another time. That doesn't change the rights of existing licensees, but there are a few ways that it could be advantageous to the owner. A public domain work has no owner, and there are no rights in it to license under any terms.


Does 0BSD/0MIT abandon the copyright?

If a jurisdiction doesn't permit public domain, there's no way to dedicate the work to the public domain in that jurisdiction. The law forum has an answer that discusses the possibility of dedication to the public domain in the US Federal law context in detail: https://law.stackexchange.com/a/65152/1219.

The answer in the law forum contains a citation to Abandoning Copyright, which summarizes the confusion and uncertainty in copyright abandonment. One paragraph of the article reads:

A number of courts have considered whether oral or written statements that purport to disclaim copyright amount to abandonment. For the most explicit statements, courts have generally found that abandonment has occurred. But because abandonment turns on the subjective intent of the rights holder, even verbal communications are often open to competing interpretations. In some instances, we identified courts that were too eager to find abandonment. Others were reluctant to deem a work abandoned despite what we believe is clear evidence of intent.

Section "a. Verbal Disclaimers" on page 541 contains several examples, which would be helpful to read to have a general feeling of what may be seen as abandoning copyright and what may not.

Given this uncertainty and confusion (likely caused by the lack of legal development in this area), and that some choices of words ("copyright", "permission", "granted") of 0BSD/0MIT are against public domain dedication, practically I don't think these two licenses implies dedication to the public domain.

Assuming no copyright abandonment, is 0MIT/0BSD identical to the public domain?

At least Copyright Act § 203 may make a murky difference in the US. US Copyright Office contains the following explanation: https://www.copyright.gov/docs/203.html

Section 203 of the Copyright Act permits authors (or, if the authors are not alive, their surviving spouses, children or grandchildren, or executors, administrators, personal representatives or trustees) to terminate grants of copyright assignments and licenses that were made on or after January 1, 1978 when certain conditions have been met...

Based on my own reading of Section 203, for some works, the conditions do not seem to be hard to meet.

Note: This answer does not discuss in the context of jurisdictions outside the US. This answer also does not discuss other intellectual properties, such as patent and trademark.

  • So that's a no? Because the license clearly doesn't abandon, disclaim, or terminate the author's copyright? Commented May 4 at 9:12
  • @curiousdannii I added one sentence to the answer at the end of the first section.
    – xuhdev
    Commented May 4 at 19:24

Should the MIT-0 and 0BSD be considered public domain declarations? Or do works released under them remain under copyright, just with the author giving them away with no restrictions? Or are those two things basically legally identical in most countries?

I think this may reflect some confusion about the way that Wikipedia article uses the phrase "public domain equivalent."

Wikipedia is not a law textbook. It is not trying to exhaustively explain the complicated legal details of the public domain (at least in that article, anyway). The term "public domain equivalent" has a pragmatic, results-oriented definition, which seeks to avoid legal complexity in favor of a simple "What can I do without getting sued?" approach to the problem.

Under this approach, a "public domain equivalent" license is just a license where (to a first approximation) you can do whatever you want without getting sued. It is called "public domain equivalent" because the public domain shares this property (of being able to do whatever without getting sued). You can't get sued for using works in the public domain, because they have no copyright to infringe. You can't get sued for using works under "public domain equivalent" licenses, because no matter what you did, the license allows it.

As the Wikipedia article briefly alludes to (and as both of the other answers acknowledge), some jurisdictions do not provide for "real" public domain dedications at all, and other jurisdictions leave them in a legally uncertain position. "Public domain equivalent" licenses are designed to achieve a status as close to public domain as possible, without requiring any provision that might be legally questionable.

This also means that such licenses are inherently limited by what the jurisdiction allows. In jurisdictions that provide for inalienable moral rights, you can't waive them, because that's what "inalienable" means, so reusers are required to respect those rights regardless of what the license has to say about it. The US does have waivable moral rights for works of visual art, but waivers must be specific to each use, so this is also a problem in that jurisdiction. The US, as described in greater detail in xuhdev's answer, also has inalienable termination rights for any copyright that was not a work for hire, and licenses can't waive those rights either. Of course, both of these limitations can affect any copyright license, not just public domain equivalent licenses.

The other, perhaps thornier issue is that moral rights are, in most jurisdictions, entirely separate from copyright, so even a "real" public domain dedication (if it were effective) might not fully extinguish them anyway. Termination rights are also notionally separate from copyright, but it is hard to see how a termination right could be exercised when the underlying copyright no longer exists.

Finally, common law countries might allow equitable defenses in any situation where this distinction becomes legally significant. If I license a work to you under a highly permissive license, and then later sue you for violating some ancillary right, you might (for example) have a defense of promissory estoppel, or some other remedy. This is in recognition of the fact that you relied in good faith on my representation about the permissiveness of the license - the court may decide that I am not allowed to "go back on my word" regardless of what rights the law may recognize. On the other hand, it is generally preferable to stay out of court altogether, and so a prudent copyright lawyer would likely advise you to avoid getting into this mess in the first place.

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