How can I find out if extracting Microsoft Word 2019 thesaurus (for another person by a freelancer) is legal or (very likely) not?

I tried searching in Google, but this question seems to be not very easy to answer.

The client says that it is allowed by a "derivative works law", and that he is allowed to create a new thesaurus based on an old one, and he will be adding more words to it and taking some out.

  • 12
    You consult a lawyer. Needless to say, the client is clueless here. Commented Aug 23, 2021 at 7:43
  • You may be interested in learning about transformative works, which, unlike derivative works, are generally allowable under copyright law. Note, however, that what the client is proposing is absolutely not an example of transformative use. Commented Aug 23, 2021 at 19:41
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    @Dan Henderson that is too broad a statement. First of all, being "transformative" is only relevant to fair use decisions, which means only under US copyright law, not the law of any other country. Second, being transformative is only one of the factors, and not even one of the statutory four, which may be considered in fair use decisions. Being transformative is by no means a guarantee of fair use status, even under US law. Commented Aug 23, 2021 at 20:07
  • As far as I'm aware, allowing derivative works is something you find in certain copyleft licenses, not so much in the copyright law.
    – corsiKa
    Commented Aug 24, 2021 at 17:14
  • @DavidSiegel I guess I should have said "may be allowable under US copyright law." Commented Sep 7, 2021 at 16:16

4 Answers 4


Your client is confused about how copyright law works (at least in the United States and virtually every other country I've ever heard about copyright in).

If I were guessing, they read something like this from the United States Copyright Office:

The copyright in a derivative work covers only the additions, changes, or other new material appearing for the first time in the work. Protection does not extend to any preexisting material, that is, previously published or previously registered works or works in the public domain or owned by a third party.

and figured that because it's a derivative work, the copyright only covers the additions and changes they make, and there's no copyright protection for the original work.

This misunderstands the law: the original work still has its own copyright (assuming it hasn't expired), and permission from the holder of the copyright on the original work is required to create that derivative work in the first place*. The copyright on the derivative work is separate—that is, both copyrights exist in parallel.

* Some exceptions, such as fair use, exist, but would be unlikely to apply to the situation you describe.

  • 4
    Probably a good idea to cite 17 USC 106(2) which explicitly prohibits precisely this. Commented Aug 23, 2021 at 19:56
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    Nevertheless, a thesaurus is subject to the limiting principles discussed in Feist v. Rural under US law. In particular, facts may not be copyrighted, and the copyright in a collection of facts is extremely weak (particularly if you replace some of the facts with different facts, as the question proposes). The client may be right for the wrong reasons.
    – Kevin
    Commented Aug 23, 2021 at 23:46
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    @Kevin That's an interesting thought. It certainly wouldn't cover anything like the definitions that some thesauruses have (I don't have a copy of Microsoft Word to check). I could imagine the selection of synonyms being arguably a creative work, since it entails editorial decisions of which words are actually synonyms, how close words need to be, etc.—similar to copyright protection for compilations. Contrast that with, say, a map, which entails no such creative decision-making, just measuring existing features. Overall, I suspect it'd be subject to copyright anyway, but I'm not 100% sure.
    – Ryan M
    Commented Aug 23, 2021 at 23:52
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    @RyanM: I agree that this is definitely a gray area. If OP is serious about it, they should probably consult a professional copyright attorney.
    – Kevin
    Commented Aug 23, 2021 at 23:55
  • 1
    @DJohnM there's a term for it: "copyright traps"
    – Andrew T.
    Commented Aug 24, 2021 at 13:38

This would be a violation of copyright (your client creating the derivative work) and likely be a violation of the EULA (extracting and distributing parts of the software).

Creating work based on a piece of copyrighted material is known as a derivative work. Doing so without permission of the copyright holder is a breach of copyright and could result in legal action from the copyright holder.

  • Are you sure creating the derivative work would be a copyright violation? Wouldn't the distribution of the work be the violation? I never heard that creating alone can already be violation.
    – blues
    Commented Aug 23, 2021 at 13:50
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    @blues It's in the name - copyright gives the right to copy, how that copy is distributed is irrelevant. Non-distributed, personal-use copies or derivatives are unlikely to result in legal action from the copyright holder simply due to their obscurity, but they still violate the original copyright. Commented Aug 23, 2021 at 14:28
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    @blues merely creating a derivative work without permission is an infringement, even if it is not distributed, see my answer. An undistributed personal derivative work is not likely to be the subject of a suit, because the copyright owner will never hear of it, and it might not be worth the expense of braining suit anyway. Commented Aug 23, 2021 at 14:47
  • @blues It would be nonsensical if there was no copyright protection until the "moment when distribution occurs" (even if you could define that concept precisely). For example, if a publishing company has completed 99% of a new dictionary, but not yet published it (for the obvious reason that it is not yet complete) it makes no sense that somebody could copy the 99% and use it in any way they wished, with no legal consequences.
    – alephzero
    Commented Aug 23, 2021 at 16:24
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    Is it necessary to point out that if you don't tell anyone about your derivative work, they can't sue you because they don't know it exists? Commented Aug 25, 2021 at 1:03

The client is mistaken. There is no such thing as "derivative Works law", at least not in the sense that the client suggests; there is only copyright law.

US Copyright Law

17 USC 106 says:

Subject to sections 107 through 122, the owner of copyright under this title has the exclusive rights to do and to authorize any of the following:


(2) to prepare derivative works based upon the copyrighted work;

17 USC 101 defines "derivative work" as:

A “derivative work” is a work based upon one or more preexisting works, such as a translation, musical arrangement, dramatization, fictionalization, motion picture version, sound recording, art reproduction, abridgment, condensation, or any other form in which a work may be recast, transformed, or adapted. A work consisting of editorial revisions, annotations, elaborations, or other modifications, which, as a whole, represent an original work of authorship, is a “derivative work”.

Note that merely creating ("preparing") a derivative work without permission is an infringement of copyright, whether or not it is then published or otherwise distributed; the comment to another answer is incorrect about that.

Moreover, the process of "extracting" the thesaurus would almost surely be copyright infringement itself, the making of an unauthorized copy, quite aside from any issue about the derivative work. If a consultant was hired to do such extraction, the consultant would be committing copyright infringement, and could be successfully sued by the copyright owner, if the owner became aware of the facts. US Statutory damages can be as high as $150,000 per work in cases of willful infringement. ($30,000 per work if not willful.)

The answer by Ryan M gives a plausible way in which the client's confusion might have occurred, but there are many serious misconceptions about copyright floating on the net.

Berne Copyright Convention

Article 1 of the Berne Convention (more formally the "Berne Convention for the Protection of Literary and Artistic Works") says, in relevant part:

(3) Translations, adaptations, arrangements of music and other alterations of a literary or artistic work shall be protected as original works without prejudice to the copyright in the original work.


(6) The works mentioned in this Article shall enjoy protection in all countries of the Union. This protection shall operate for the benefit of the author and his successors in title.

Almost every country in the world has signed and ratified the Convention. (Many of those that have not have signed the TRIPS agreement, which includes most of the protections of Berne.) While the details of copyright protection, and any exceptions to copyright are specified in the laws of individual countries, and differ from country to country, the making of derivative works is an infringement in every country that adheres to the Berne Convention, and so is the making of unauthorized copies. The operations described in the question would not be lawful (without permission from the copyright holder) in any country that adheres to the Berne Convention.

As the Wikipedia article on the Convention says:

Subject to certain allowed reservations, limitations or exceptions, the following are among the rights that must be recognized as exclusive rights of authorization:

  • the right to translate,
  • the right to make adaptations and arrangements of the work,


  • the right to make reproductions in any manner or form ...


In short, there is no general right to make derivative works from copyrighted originals without permission. Doing so is infringement, and can lead to a successful suit for damages. Damage amounts will depend on the law of the country where suit is brought, but can be sizable. A consultant who assists in this process might also be subject to suit.


Derivative works add protection, they don't remove or replace any.

If work X is created by A, then A gets protection for unauthorized use of X.

If work Y is created by B as a derivative of X, then:

  • A still has protection for unauthorised use of X, including as part of Y

  • B gets protection for unauthorised use of Y

    |   Derivative work Y      |
    | +----------------------+ |
    | |  Original work X     | |
    | | copyright owned by A | |
    | +----------------------+ |
    |   copyright owned by B   |
    | on the differences only  |

So to distribute Y, one would need authorisation from both A and B.

Otherwise it would just be too easy: I take Avatar, I replace one pixel in one frame of the picture, and voilà! it's a derivative work and now I can distribute it without paying anything anyone? Of course not!

Usually B will get authorisation from A so they can authorise users to use Y, including the parts of Y which are X, without having to get authorisation directly from A as well, but it's just an indirect way of achieving it.

In this case, it's more than likely that the thesaurus is not actually an original work of Microsoft, it's more probably something they bought themselves.

Also note that whether extracting and modifying the therausus per se is illegal probably depends on the country and whether it is locally considered software, a database, or some other form of protected material. If it's for their personal use only, it may be allowed by law, though it may be forbidden by their contractual agreement with Microsoft (the EULA). If it's for distribution (and even distributing internally inside a company may count), it's most probably not allowed at all without authorisation from Microsoft.

Of course, your client giving you a copy of Word and you sending them a copy of the thesaurus after having extracted it is also protected, and you are most likely not allowed to do it.

  • 1
    One pixel in one frame, maybe not. But if you make all the blue people green instead....
    – phoog
    Commented Aug 24, 2021 at 2:38

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