If a minor releases software under a FOSS license, is the license binding? Could the minor sue a violator?
A contract with a minor is valid until the minor or their legal guardian void the contract. The contract can be void until some time after the minor is not a minor anymore. So for the question that you asked, definitely yes, a minor can sue a violator, or at least their guardian can.
The other way round is problematic. The idea behind contracts with minors being voidable is that an adult can easily talk a minor into entering a contract that is against their interests, and the law wants to protect these minors.
Let's say you are a minor. You wrote this excellent software that I would be absolutely willing to pay you $100,000 for. But to save the money I advice you how great it would be if you published this software as open source under a FOSS license (so I can use it without paying). Next week your parents find out. If it was a contract, then they could void the contract. But since it is a license... That's tricky. If your parents told me that they voided the license and should either pay up or get sued for copyright infringement, the idea behind the law is that they should be able to make me pay or sue me, but I'm not sure what a judge would think about that.
The consequence is that I wouldn't want to rely on a FOSS license when the copyright holder is a minor.
Now the question in your title: Can minors publish open source software? Answer: Absolutely yes, but as a potential user of that software I would be weary as long as they are minors.
This topic might not have a clear answer, but it looks like FOSS licenses aren't clearly considered contracts:
Historically, some open source vendors and enthusiasts insisted that such arrangements were merely limited licenses to use the software and not contracts in part because they do not require the copyholder to furnish consideration to support the grant of use. If the user violated the restrictions in the license, licensors could seek redress in an intellectual property infringement proceeding, but not for breach of contract.
Many early objections to open and free licensing schemes opined that these licences were invalid because there was no consideration, they were pretty much offering software for free.
Although they are not considered to be contracts, properly drafted open source licences are legally binding and enforcement action can be taken against those who breach them. This may be under contract or copyright law, depending on how the licence is framed. No-one is forced to explicitly accept the licence, but implicit acceptance of the licence conditions is the only route to legitimate use under copyright law.
– Rowan Wilson, OSS Watch […] is a team of experts in free and open source software providing an independent, non-advocacy advisory service based at the University of Oxford.
There have been a number of court opinions made on OSS licenses including on appeal:
We consider here the ability of a copyright holder to dedicate certain work to free public use and yet enforce an "open source" copyright license to control the future distribution and modification of that work. […] Jacobsen brought an action for copyright infringement and moved for a preliminary injunction.
The District Court found that Jacobsen had a cause of action only for breach of contract, rather than an action for copyright infringement based on a breach of the conditions of the Artistic License.
The District Court's interpretation of the conditions of the Artistic License does not credit the explicit restrictions in the license that govern a downloader's right to modify and distribute the copyrighted work. The copyright holder here expressly stated the terms upon which the right to modify and distribute the material depended and invited direct contact if a downloader wished to negotiate other terms.
It is my opinion based on the above that a violation of an OSS license would likely be treated as a copyright violation. The holder of the copyright could sue for copyright infringement, the outcome of which would depend on the specific wording of the license chosen. So...
Can a minor claim copyright? Minors may claim copyright, and the Copyright Office issues registrations to minors, but state laws may regulate the business dealings involving copyrights owned by minors. For information on relevant state laws, consult an attorney.