Let's say I invent a new image file format and release the specification to the public. Is it possible to only allow GPL projects to implement this specification? Or is this not possible in the U.S.? (Because the national laws do not allow something like this. To keep it simple let's assume we are in the U.S.)

There is a similar question here but it is not the same because it is about a reverse-engineered file format.

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    Does conforming to the specification require structure or processes that are patented? A way to think about the question is - what IP does the creator of the specification have? The exhaustive list is patent, copyright, trademark, trade secret. Commented Nov 7, 2022 at 17:45
  • @GeorgeWhite I think patent is the keyword. Is it possible to register a patent while still allowing GPL projects to use the specification for free? Why isn't it enough to state in the specification "this spec may only be implemented by GPL projects"?
    – zomega
    Commented Nov 7, 2022 at 18:56
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    You may also want to check Open Source SE
    – sourcream
    Commented Nov 7, 2022 at 19:03
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    A patent owner can license its use conditionally similar to a copyright holder licensing its use. Commented Nov 7, 2022 at 20:38
  • You would not be able to enforce a copyright on a "specification". You can copyright the actual publication or a "book" in which the specification is described, but you cannot copyright the rules of the specification. In some cases protocols have been patented, but you are not asking about a patent.
    – Cicero
    Commented Nov 7, 2022 at 21:47

1 Answer 1


Unless you have a legally valid IP right related to the specification that statement is meaningless. When a software license is granted it is based on the copyright of the code. The copyright of the spec. just stops people from copying the spec - it does not protect the information in it.

You can restrict copying of the spec. under copyright, you can make up a name for the spec (like USB or Bluetooth) and get a trademark and only allow the trademark use in limited cases(doesn’t stop implementation of the spec), or get a patent that would be necessarily infringed if something complying with the spec was created and used, sold, made, etc. or you can keep it secret and only show it to people who contractually agreed with your terms.

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