Is this copyright infringement? Location: United States Given that copyright does not protect ideas Let's imagine app a and app b. These two apps are created by two different people. No patents are involved. The person that created app b had access to app a's full source code before working on app b. These two apps do the same thing. App a has 10 features. App b copied all 10 features from app a, but expressed all features in a different way where there is no substantial similarity. Would App b be copyright infringement?
The other answers get at this somewhat obliquely, but to be clear your assumption 7, that there is no substantial similarity, implies no infringement. Substantial similarity is an element of infringement. But it is also often a disputed element. On your fact pattern, it might even be the only disputed element in the case, and in a close case in a technical area such as this (where it would likely seem to a judge that it could go either way), a jury would simply vote on it. That is, no oracle of copyright doctrine would be consulted for &quot;the answer&quot; to the question of substantial similarity; a jury would just hear testimony from both sides and get some instructions from the judge on the applicable standard (which are rarely much, if any, help) and vote. Substantial similarity - that is, similarity that appropriates &quot;enough&quot; of the original work to be actionable - is very difficult to assess in any objective manner. This aspect drives many creative people in copyright-intensive specialized disciplines (such as software and music) crazy. Often when people have expertise in an area, it may seem &quot;obvious&quot; to various individuals what ought to be actionable and what shouldn't. But it is rare to find complete conensus. (Most copyright infringement cases involving music - e.g. the one involving Katy Perry's &quot;Dark Horse&quot; or Robin Thicke's &quot;Blurred Lines&quot; - attract a lot of attention because juries end up voting on an issue that almost anybody who has heard two songs could form an opinion about, and maybe a strong opinion about.) A loose analogy to your question would be in the criminal context, where the fact pattern is, so let's say A kills B, but didn't intend to, did A commit murder? In most jurisdictions the formal legal answer to that question would be &quot;no, of course not, because intent is an element of the crime of murder.&quot; But in many murder cases intent is a highly disputed element (sometimes the only disputed element) and in close cases a jury just gets to vote on what they think from their understanding of the facts, or at least what is presented to them as the facts in court. (The standard of proof in criminal cases is formally different but in practice I am not sure it is at all different.) As another answer suggests, the fact pattern you describe sounds kind of &quot;fishy,&quot; and while that does not doctrinally matter, let alone settle the issue, it might matter to a jury. Two cases somewhat along these lines are Google LLC v. Oracle, Inc. (which involved basically this fact pattern, with Google in the role of &quot;app b&quot;) and Lotus Dev. Corp. v. Borland Int'l., Inc. (with Borland in the role of &quot;app b&quot;, although the copying that occurred was not at the level of source code). They were both ultimately decided on other grounds (and the relevant issues only got to a jury in one of them), but in a world where other statutory defenses had not been asserted they both could have been decided simply by jury vote.
That would be pretty much a classical case of copyright infringement. Drawing a thing from memory is copying just as much as drawing a thing with the original before you or xeroxing a thing. The degree of match between the original and your copy may vary depending on how good your memory is, but that doesn't matter, because copyright protection is not about "making exact replicas", it is about copying in any form.
Software doesn't infringe any patents. Creating a product that includes the software may infringe the patent, and may infringe that patent because the software is included, but the software itself doesn't. Software on its own doesn't have any effect that could be patented, only as part of some machine. On the other hand, if you want to distribute software that is under the GPL v3.0 license, then a requirement is that you give everyone a patent license for all patents that would be infringed by using the software (as part of some machine), and if you are not the patent holder, then in practice that means you are not allowed to distribute the software. With your grand plan that you write software and then let the end users do the patent infringement, that will backfire in two ways: First, you'd be likely sued for contributory patent infringment, because it is you who enables the patent infringemnt. Second, you can be sued for copyright infringement because you have no license that allows you distribution of the software, depending on the Open Source license used.
If you want to implement this or a similar feature, you'd look up the patents, and either get a license (unlikely that Microsoft would give you a license), or figure out how to implement the feature without violating the patent. An example how a company I worked for worked around a patent: In order to compress data. in the best possible way, the idea was to try eight different methods to compress the data and pick the best compressed data. There was a patent for that (even though to me, this was quite obvious). Workaround: The software tried eight different methods and reported a number from 1 to 8 indicating which method gave the best result (unlike the patent, which actually gave the best result). Then the data was compressed once using the best method. No patent violation. You'd probably want a patent lawyer to check if your idea how to implement the feature violates the patent or not, and how to get around it. It takes a specific mindset that you and I don't have. And even good lawyers who are not patent lawyers might not be able to help you there. Commercial vs. open source/free software makes no difference, except that Microsoft might not bother suing you if there is no money to be made. Unless the intent is to prevent you from implementing the feature, in which case the would sue companies without money as well.
Both the displayed site (including all text and images) and the html, css, javascript and other code that generates the display are protected by copyright. This is true in pretty much every country. You would not be able to reuse them lawfully without permission, unless an exception to copyright applies. If no exception applies, and you have not obtained permission, this is copyright infringement. In most cases copyright infringement is treated as a tort (a civil matter), not as a crime. This means that law enforcement generally will take no action and have no interest in such a situation. The copyright owner could sue for infringement, and possibly collect money damages. In the US, statutory damages can be as high as $30,000, or up to $150,000 for &quot;wilful&quot; infringement, or as low as $750 (per work infringed). Or actual damages can be collected instead. In other countries, actual damages plus costs of suit are more likely, but the rule can be different in each country. The possible exceptions to copyright vary significantly in different countries. In the US the major exception is Fair use. See Is this copyright infringement? Is it fair use? What if I don&#39;t make any money off it? and I have a question about copyright. What should I read before I ask it? for more information In general short snippets of code can probably be used under fair use, but substantial parts of the code or the displayed site are less likely to qualify as fair use. And if it is illegal then why are there so many legal open source or paid software and applications for cloning of website like httrack, cyotek, webcopy etc? Most of these tools have legitimate uses, including learning how a site is constructed without distributing copied content; and cloning or partial cloning of a site with permission. Even if the tools were mostly used for unlawful copying, that might well not be a high priority for law enforcement, and cross-border law enforcement (which this in many cases would involve) is often much harder for the police and other authorities.
It's possible that CAD has a separate licence from the authors of ABC that allows them to produce a closed source copy. If not, they have no right to distribute CAD. However two wrongs don't make a right, and so you don't get to violate the copyright of CAD.* Unfortunately, unless you are one of the authors of ABC, you have no standing to sue the authors of CAD. You can only notify the authors of ABC and hope they do. If the authors of ABC don't have the resources to pursue the matter, you may be out of luck. That's one of the reasons the FSF gets copyright assignments for their projects. * It turns out that this is a much more debateable issue than I first thought. Some courts have held that an unauthorized derivative work is not copyrightable.
The question as worded implies that if something is a parody it is automatically fair use or allowed in US copyright law. This is a myth. First of all, in a copyright context, the term "parody" is somewhat limited. In that sense, a "parody" is a new work which comments on the original (often but not always by mocking or ridiculing the original). A mere alternate version which modifies the form of the original, perhaps humorously, but not to comment on the original or perhaps on much of anything, is not a parody. A new work which modifies the original to comment on something else, but not on the original, is a satire. Of course many works may be both parodies and satires in this sense. See this law.se Q&amp;A for extensive quotes from Suntrust Bank v. Houghton Mifflin Co 268 F.3d 1257 (The case of The Wind Done Gone vs Gone with the Wind) and discussion of what is and is not a parody in US copyright law, and when a parody is fair use. A parody, because it comments on the original, will often be found to be a fair use of the original. But not always. The full four-factor analysis must still be done, and the results are never certain until a court has passed on the specific case. See this law.se Q&amp;A for more on fair use. I can't tell from the question whether the modified song is truly a parody in the sense used in copyright law. If not, it probably isn't fair use, although it might be for other reasons. By the way, a song written for a television show or video to be distributed commercially is a commercial use, even if a non-profit corporation is involved, and even if there is an educational purpose. Note that fair-use is a strictly US legal concept. Even if something is fair use under US law, it may be copyright infringement under the laws of some other country.
Algorithms are not subject to copyright. A particular implementation can be copyrighted, but an algorithm itself can't be copyrighted. Someone re-implementing the algorithm with their own code has done nothing to give you copyright claims against their work, and is not bound by any software license you use. That's what patents are for.