Proving ownership of a pseudonym Suppose I have written a literary work (an article, some source code, etc.) and published that work under a pseudonym. Suppose also someone else is infringing upon my copyrights and I want to sue them because they are not responding to more friendly requests to come in compliance with the license. The question is, in what ways can I prove to the courts that I am in fact the copyright holder (i.e. I have a better than 50/50 chance that the court holds that I am the same person as referred to by the pseudonym mentioned in the copyright line). In case it matters, I have not bothered to register my copyrights with any copyright office and I am interested in jurisdictions that follow the Berne Convention.
If the suit is to be filed in the US, the first step is to officially register the copyright. No US copyright infringement suit can be brought until the copyright has been registered. The registration process includes a formal declaration as to who the author is (or authors are). (I believe this statement is made under penalty of perjury.) Once the registration issues, the certificate of registration is admissible evidence of the facts stated in it in a us court. Indeed 17 USC 410 (c) provides that: (c) In any judicial proceedings the certificate of a registration made before or within five years after first publication of the work shall constitute prima facie evidence of the validity of the copyright and of the facts stated in the certificate. The evidentiary weight to be accorded the certificate of a registration made thereafter shall be within the discretion of the court. In other countries, the testimony of the plaintiff in a copyright infringement suit is itself evidence that the work was created as stated. In either case, it is possible for the defendant to challenge the assertion and claim that s/he is the actual author. Showing when and where the work was first published can usefully corroborate the plaintiff's testimony. Having included a copyright notice in the initial publication may be of value, but if the notice only lists the pen name, it is not of much value. Records of the platform on which a work has been published may help in verifying the identity of the author. So may the testimony of others who saw or read the work, or who were told about it by the author. An author's own copies may be of value, if they carry a timestamp, as computer files generally do. But computer timestamps are not usually secure. Timestamps on email generally are reasonably secure, and could establish that the content existed and had been transmitted on a specified date by a specified person. But none of this will matter unless the defendant claims that the plaintiff is lying in claiming authorship. Unless that happens, the plaintiff's testimony will usually settle the matter. A person whose work seems to have been infringed would usually be wise to consult a lawyer with experience in copyright suits. Such a lawyer could advise if it is wise to bring suit at all, and if it is, what evidence will probably be needed.
There is no US law licensing journalists or people who report the news, or requiring such people to identify themselves by legal name. Nor can there be under the US First Amendment. There is also no law requiring a person to identify himself or herself by legal name online. Some sites, including Wikipedia, have policies against having multiple undisclosed user IDs for the same person, but that is a matter of the site's own rules, not a matter of law. Any US law mandating this would again run afoul of the First Amendment to the US Federal Constitution. This article on Anonymous Speech reviews and cites a number of US Supreme court cases on the subject of anonymity, mostly in political contexts. This article from the Electronic Frontier Foundation (EFF) discusses the same general subject. Both articles mention that The Federalist (analyzing and advocating for the then-unratified US Constitution) was originally published under the pseudonym "Publis". The EFF Article "Court Recognizes First Amendment Right to Anonymity Even After Speakers Lose Lawsuits" discusses the 6th Circuit case of Signature Management Team, LLC v. John Doe in which it was held that an anonymous blogger who lost a copyright infringement suit could nonetheless remain anonymous. This page apparently from a Harvard course, lists and briefly describes several cases on the same subject. In Doe v. Cahill, 884 A.2d 451 (Del. 2005) an elected official sued an online poster for defamation, and sought to force the ISP involved to disclose the poster's identity. The Delaware Supreme Court ruled against this, setting a standard offering greater protection for such anonymous online speech than previous cases had. This answer is very US-centric. Laws in other countries are different. The OP has not specified a country or jurisdiction.
(Assuming the jurisdiction is the US.) Your question I was wondering whether there are any limitations on using photos of private individuals on websites. is the least of your potential problems. Photos of the public taken in public are mostly legal to use and publish, and you own the copyright on the photo, and generally don't need a model release. But your plan of posting the photo with accompanying information about (alleged) fraud: There's a fraud conducting business in my state and I want to create a website that warns others of his fraudulent practices. is potentially legally problematic. As phoog indicates in his comment, you need to be aware of defamation, both at the federal level and among states, as some have criminalized defamation (Wikipedia). Libel is the publication of provably false facts by one person about another person. For a full outline of defamation (libel and slander, and including private and public figures), see Libel and Slander | Nolo.com. What you want to do is publish "facts" about this alleged fraud on the website with a photo of the individual, linking the fraud allegations to them. That is potentially libelous. The facts of the fraud may be provably true, or they may be provably false; that remains to be seen. But the facts don't matter when considering what actions the person can take against you if you publish such information on your website. If this business and the individual(s) feel they are not committing fraud, they can sue you for libel in civil court, alleging that you have damaged their reputation and impacted their business by publishing those facts on your website with the photo identifying the person and their business. If they take legal action, and you can prove the business and the individual(s) are committing fraud with provable facts - hard evidence of fraud, such as legal documents and court judgments - than you should (no guarantees) be able to successfully defend yourself in a libel suit brought against you by that person. Even if the business and the individual(s) are aware of facts that prove their fraud, and know they will probably not prevail in court, they can still take you to court, and it will cost you whatever time and money it takes to defend yourself. My responses above concern what legal actions the alleged could take against you if you published the website with the photo and information about the alleged fraud. No one here is advising you to put up the website with the photo and the "facts" as you see them, even if you have hard proof of the facts of the fraud; you should find legal representation before taking any action with the website. And, no one here is advising you to open any legal action against the person; that's your choice in terms of determining your case and if you can show actual harm that was caused by the alleged fraud by the individual, and you should find legal representation before taking any action.
Copyright in the US is usually a civil matter. Meaning that the copyright owner can sue (typically for money damages or injunctive relief) an infringer. The criminal laws that we have are aimed at the reproducer and/or distributor. In other words, chances are that you won't get in any criminal trouble for accessing academic articles of dubious origin. But never say never. RIP Aaron Schwartz.
Do you have an explicit permission by the artist? Does the artist give a blanket permission to anyone which covers this kind of use of their work (a license)? If no, then you commit a copyright violation when you use their work for your blog. This applies to practically any country which signed the Berne convention which is almost everywhere in the world. Having no commercial interest is usually not an excuse to violate copyright. Regarding which jurisdiction applies when you, your website and the copyright holder are in different countries: I opened a new question about this.
There are jurisdictions that do not allow authors to place their work in the public domain, such as Germany. Main reason is the strict monistic approach the German copyright law bases on. Key feature of this approach is the concept that, in principle, the copyright/author’s right itself can neither be transferred to another person nor waived by the author herself. The German author’s right consists of two parts, the moral rights and the exploitation rights. The moral rights are – as a rule – personal rights that are bound to the person of the creator (or, after her death, her legal heirs), i.e. they can neither be transferred nor waived. Since moral and exploitation rights are considered as inseparable parts of the author’s right as a whole (monistic approach) the exploitation rights cannot – in principle – transferred or waived by contract as well. CC0 is supposed to get you as close to the public domain as possible in your legal system. CC0 helps solve this problem by giving creators a way to waive all their copyright and related rights in their works to the fullest extent allowed by law. CC0 is a universal instrument that is not adapted to the laws of any particular legal jurisdiction, similar to many open source software licenses.
As @amon stated in a comment, copyright requires creativity. If the author of a tool wants to claim copyright on the output of that tool, then that output must contain something that required the creativity of the tool author. For a tool that just re-indents its input, the output is created from the input with a mechanical, non-creative, transformation and the output does not contain any creative content that wasn't already present in the input. For that reason, authors of such tools can't claim any copyright on the output. For a tool like bison, which was mentioned in the comments, the output contains a measurable amount of creative content that was not present in the input, but which was provided by the authors of bison. For that reason, the authors of 'bison' do have a copyright claim on the output of the tool (for which they give a broad permission to use). So, the basic question becomes, how much of the (creative) content of the output can be traced back to the tool itself and not to the input that the tool processed. For linters/formatters, that is likely to be very little. For code generators, it can be anywhere between very little and all of the output. The license restrictions on the code produced by the tool itself are by default the same as the license restrictions on the source of the tool, but the tool author can choose to apply any other license to the tool code that ends up in the output. If the output of the tool is, at least in part, dependent on an input file, then the authors of the input file also have a copyright claim on the tool output (as their creative work influenced the output), so the tool author can not claim exclusive ownership. The usual situation is that for tools that don't add creative content to the output, the author explicitly states that the don't have any copyright claims on the output. For tools that do add creative content, that content might be released under very permissive conditions (like, "you can use the output as a whole for any purpose, but you can only separate out the code that comes from the tool's codebase if you adhere to the &lt;X> license")
The first thing that has to be done (in court, or via lawyer-to-lawyer communication) is that The Company has to prove that they own the copyright. If they accomplish that, you can defend yourself by providing proof of a license to download and redistribute. From what I can tell, you cannot directly prove that, since the rights-holder did not give you the license. The issue is that a third party cannot impose a license on a work simply by putting it out there with a file that claims to be a license from the artist. So this brings in the Free Music Archive: they presumably have some evidence that the rights holder did indeed grant the alleged license, and may be able to provide proof. Your argument may be credible, in the sense that you had a good-faith belief that the item was so licensed, and the website would provide a basis for concluding that that belief is reasonable. If the work was licensed, then the some rights holder would know that, but not necessarily the current one. Assume the artist made a recording, transferred the rights to Company A, who later sold the rights to Company B who is now coming after you. Artist may have licensed it when it was his, and forgot to tell A. A may have licensed it when they sold the license to B. Artist may have improperly licensed it after he sold the work to A (under the "I wrote it, I have the right to do whatever I want" non-legal theory). A might have improperly licensed the work after selling the right to B (maybe by mistakenly including it in a package deal, i.e. via bookkeeping error, rather than ignorance of the law). Or, they may simply have forgotten. If this is a DMCA takedown notice, the notice-giver could just be abusing the system. But we don't know how you were contacted, so I'll leave DMCA out of this for now.