I am building a website that will allow users to enter preferences for certain things (we'll call them cars), and get suggestions for other "cars" that they may be interested in. Finding similarities between the "cars" requires a very large data set on the characteristics and features of "car" models.

I've collected a significant amount of this data, much of which is public domain. I intend to use it in a proprietary, commercial project, which is fine so far.

However, one of the data sets I'd like to use is released under the GNU Free Documentation License. I've read through the license, and I'm unsure how its terms about "modification" and the like apply to this situation. I don't really want to modify the original document (the data), I just want to read it and process it as part of a larger project. I'd certainly be happy to re-distribute the data freely as part of my work.

Is this allowable under the GFDL terms? Would my new project have to be GFDL? Would that even make sense since it's a software project, not a documentation project?

I'm hazy on the difference between modifying the data, redistributing the data, and writing an algorithm that leverages the data to do other things...

  • Can you be a bit more specific about the GFDL data in question? a link? May 7, 2016 at 19:12
  • FWIW, as you found out the GFDL familiy of licences are rather tricky and complex. May 7, 2016 at 19:15
  • Do you plan to distribute any of the information contained in the GFDL document to end users, or only use it privately on your server to make decisions? If you don't distribute any part of the document in any form to another person, then the license doesn't really stop you from doing anything.
    – apsillers
    Aug 23, 2016 at 17:44
  • The question is hazy (perhaps intentionally so), but you probably want to make a distinction between the software and the data it processes. Perhaps if you can explain that more clearly, the answer will be more obvious. In particular, distribution arrangements probably matter.
    – BradHards
    Nov 17, 2016 at 0:37

2 Answers 2


Almost every section of the GFDL has something prohibiting this.

2. Verbatim Copying

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that...you add no other conditions whatsoever to those of this License.

Which you plan to do in your proprietary work.

1. Applicability and Definitions

A "Modified Version" of the Document means any work containing the Document or a portion of it


4. Modifications

You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License

Your database will likely be a work containing the Document or a part of it, so this section comes into play.

5. Combining Documents

You may combine the Document with other documents released under this License under the terms defined in section 4 above for modified versions

Combination just refers back to sections 1 and 4, so it doesn't help you either.

6. Collections of Documents

You may make a collection consisting of the Document and other documents released under this License...provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

And collection just refers you back to section 2.

7. Aggregation with Independent Works

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

You intend to include the GFDL data in a proprietary work that limits users' rights to the rest of the data contained therein, which this section does not permit. The implication of this section is that the license must apply to the other works if the collection cannot be defined as an "aggregate".

So I'm sorry to say that you'll have to do without that data unless you want to release your entire program under the GFDL. Unless you want to face section 9:

You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.


If you are just using the knowledge of this database without presenting part of the content to the user, it should be fine IMHO. Bare-knowledge is not copyrightable, only its creative expression is.

Notice how Google uses tons of knowledge it gathers on the web (images for instance) to train its machine learning/AI algorithms. As long as it does not mean presenting any copyrighted content to a user, this is perfectly fine.

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