Reference The post that started it all

In order to clear up the original question I asked in a provocative manner, I have posed this question.

If you learn an algorithm from an open source project, is it OK to use that algorithm in a separate closed sourced project? And if not, does that imply that you cannot use that knowledge ever again? If you can use it, what circumstance could that be?

Just to clarify, I am not trying to evade a licence, otherwise I would not have asked the question in the first place.

  • 1
    You shouldn't post a question explicitly for debate. That's a sure way to fasttrack it to closure. If you want a debate, go to a forum, otherwise, you may want to rephrase. Commented Jun 27, 2011 at 22:36
  • Most algorithms are not patented. If you can find the body of algorithm on Wikipedia, then chances are good that it is not proprietary (check the corresponding article though). The patent could also expire, such as was the case with JPEG. Once you find the algorithm on Wikipedia or in other academic publication, you can usually use it. Just put some effort into writing your own code.
    – Job
    Commented Jun 27, 2011 at 22:38
  • 2
    While I did use the word debate, I do believe there is an answer to this question. I believe the debate would be formed by different answers and therefore this question is valid. Commented Jun 28, 2011 at 0:22

4 Answers 4


IANAL. If this is of great concern to you, seek the advice of your attorney.

If you learn an algorithm from an open source project, is it OK to use that algorithm in a separate closed sourced project?

Yes. An algorithm is not eligible for Copyright, so there is no Copyright issue. It is merely a sequence of steps; a recipe for arriving at a conclusion from a given starting point. Copyrights cover expressions of ideas. An algorithm is neither an idea nor an expression of one; it is merely a sequence of steps to perform some kind of work and produce some kind of result; it's a recipe or a guide.

For software to be eligible for Copyright, it must be the application of algorithms in a larger work. Your particular use of an algorithm is eligible for Copyright protection, but the algorithm itself cannot be. (You can substitute "interface" for "algorithm" and the statement holds true, at least in the US.)

The patent issue is irrelevant to the question as posed.

  • +1 For algorithms not being patentable.
    – Andres F.
    Commented Jul 26, 2013 at 20:53
  • 4
    @Andres Algorithms are patentable, but not copyrightable! Like the answer says. Patent issue is irrelevant to the question, if we assume the open source project isn't violating any patents. If it is, then you can't use it as open source, nor can you re-implement it.
    – MarkJ
    Commented Jul 27, 2013 at 7:51
  • 2
    @MarkJ True, I meant to write "copyrightable". Not sure why I wrote "patentable", since I know the difference. My bad :P
    – Andres F.
    Commented Jul 27, 2013 at 19:25
  • @MarkJ the open source project could own the patent (or a license), could it not? Commented Mar 23, 2020 at 14:48

Under US law at least, algorithms cannot be copyrighted. The only thing you have to worry about is patents and that has to actually be pursued by the author--unlike copyright that applies as soon as the matter has been published in other words.


As stated, Design Algorithms can be patented.

However, It's worth noting that design patents can only be filled for up to one year after the design/idea is first thought up or published. If the process has been out for a couple years (and no-one has patented it) then it cannot be patented now.

  • true unless a provisional patent was filed. I am not a lawyer, but as far as I understand those can be filed and refiled indefinitely and it's impossible to know if one has been filed because their contents aren't made public.
    – Ami
    Commented Jun 28, 2011 at 1:04
  • @Ami, a Provisional Patent only lasts one year. To my knowledge you cannot re-file them (though it might depend on the type of thing being patented. A Provisional Patent only "saves your spot" in the patent line while you get a real patent filed.
    – Xeoncross
    Commented Jun 28, 2011 at 16:49
  • see: wipo.int/treaties/en/ip/paris/trtdocs_wo020.html#P83_6610 article 4.C (4)
    – Ami
    Commented Jun 28, 2011 at 17:03

As I understand it the algorithm itself is not copyrightable but the expression of it in program code is. The problem you may face is if you write an implementation and parts of it up being similar to an implementation you have previously read then you may have an uphill battle to demonstrate that you didn't (knowingly or unknowingly) copy parts of the expression.

Patent issues are seperate, they apply to anyone who implements the algorithm regardless of if they have read a previous implementation.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.