When learning from different sources, some of which license their code, is re-applying those techniques and/or knowledge in my own projects considered copyright infringement

  • This answer will show you the different cases you have to consider when learning or copying from other sources. Commented Mar 14, 2023 at 7:31

2 Answers 2


It shouldn't be copyright infringement, per 17 USC 102(b) in the US. "Idea[s], [...] concept[s], principle[s and] discover[ies]" are not subject to copyright protection. While this text is specific to US law, the general notion is not, and you will find a similar limitation in the laws of most other countries, albeit with a different wording. Each country draws the line in a slightly different way, but most of them do draw a line of some sort. This is called the idea-expression distinction.

Unfortunately, we live in a society. It is easier and safer for lawyers to tell you not to do something, than to tell you that you can do something. The idea-expression distinction is a gray area, especially since not every country interprets it in exactly the same way. It has therefore become common for lawyers to recommend clean-room engineering in situations like what you describe. In this process, one team of engineers reads the source code, and then writes a specification, which is used by an entirely different team of engineers to implement their own version. The idea is to totally wall off the original source code from the development process. It must be emphasized that this is a risk-minimization strategy, not a legal requirement. The law does not say that anyone who reads the source code of program A and then writes a similar program B must necessarily infringe on A. However, it is much easier to defend this practice if the person who wrote B is not the same person who read A.

In order to prove infringement, courts (in the US) have held that two elements must be established:

  1. The defendant had access to the original work.
  2. The defendant's work is substantially similar to the original work.

The purpose of clean-room engineering is to cut off the inquiry at (1). In cases where this was not done, courts (in the US) have applied the abstraction-filtration-comparison test to decide (2). This is a very complicated and fact-specific inquiry into the exact nature and scope of the similarity between A and B. It is understandable that lawyers do not wish to litigate this test out. I imagine it would be extraordinarily expensive to brief, research, and litigate all of the relevant issues in a real court case. Other countries may not use the exact same test, but the legal issues will nevertheless be complicated in similar ways.

On the other hand, if you never read any source code at all, for fear of "contaminating" yourself, then you will likely struggle to develop as a programmer. Reasonable people do not sue each other over allegations that one engineer read three lines of code from a completely unrelated codebase six years ago. To a certain extent, this is a judgment call on your part. Do you think the person who owns that code is litigious? Are you planning on doing related work in the near future? Is the code under a relatively permissive license? All of these questions will inform your decision about how to proceed.

  • Hello sir, firstly thanks for your reply, and to make my question clear for you, the resources that I mean are Tutorials and courses, so basically and based on your last remark, I think I'm good ? Commented Mar 18, 2023 at 13:45
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    @NoureddineDebiane: I cannot make absolute promises as to who will or will not sue you. Anyone can sue anyone else for anything. If you're using the course materials in a reasonable way, then I think a lawsuit is unlikely in practice, but I am not your lawyer.
    – Kevin
    Commented Mar 19, 2023 at 19:52

Copyright law protects tangible expression, and not the idea itself.

So, if one learns techniques or knowledge from open source software, and then rewrite on their own, without copying code, that is not copyright infringement, because it is copying the idea and not the expression.

Of course, with open source software, especially those which are licensed under free permissive licenses (like 2-clause BSD, 3-clause BSD, MIT), you are also licensed to copy, use and distribute the software in any form, as long as attribution is included. In order words, both the idea and the expression can be copied, as long as there are no patents on the idea.

From the page "Idea vs. Expression – What is protected under copyright law?" by Zachary Strebeck, Attorney-at-Law:

Under U.S. copyright law, “original works of authorship” are protected for a limited time. Copyright gives the author the exclusive right to copy, distribute, perform, display and create derivative works from this original work.

Originality shouldn’t be confused with novelty, however; there is no requirement that the work has to be completely distinct from all others, like with patents. The work must merely be an independent creation of the author, even if it is substantially similar to that of another author.

The Idea/Expression Dichotomy

One sticking point that often confuses non-lawyers is the question of what is protected by copyright and what isn’t. According to Section 102(b) of the Copyright Act of 1976, no “idea, procedure, process, system, method of operation, concept, principle, or discovery” is eligible for copyright protection.

Copyright law generally protects the fixation of an idea in a “tangible medium of expression,” not the idea itself, or any processes or principles associated with it. The nuances of this distinction are sometimes difficult to grasp, and the reality of the situation is that the facts of each case have to be looked at individually. The concept works as more of a continuum than a dichotomy.

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