They can use whatever license they want, but that choice will affect who will or can use it. From the license:
> You may use or modify the software only for non-commercial purposes such as personal use for research, experiment, and testing for the benefit of public knowledge, personal study, private entertainment, hobby projects, amateur pursuits, or religious observance, all without any anticipated commercial application.
That means most people can't use this keyboard to write a work email or text message. That's a really restrictive license, and pretty unexpected for a keyboard, to limit what you're allowed to type. Pointing it out doesn't seem harsh.
I think they mean "use the software" as in using the actual source code of the software in some derivative work or as part of some other application, or downloading and redistributing it for a different purpose, and things like that, not using the end-product application. They could stand to be a lot clearer about that, but their whole goal is just to prevent mega-corporations from being able to freeload off their work to make money off their software, not to prevent random people from using their software in certain contexts that might be construed as "commercial" in some sense. They mean not using the software for commercial purposes in the sense of not selling the software, not simply not using it for business emails or something stupid like that.
The maintainer literally responded to someone else making a similar claim in this HN thread to say that this is now the meaning of that license clause. Someone else posted the Cornell Law legal dictionary definition of 'commercial purposes'. It is really annoying that people who write software suddenly think they are legal experts who can make these kinds of ridiculous claims anytime 'licenses' come up. Instead of making stuff up off the top of your head as though it was factual, please defer to experts in the field. On legal issues this is particularly annoying.
> The term “used for commercial purposes” means the carriage of persons or property for any fare, fee, rate, charge or other consideration, or directly or indirectly in connection with any business, or other undertaking intended for profit.
> You may use or modify the software only for non-commercial purposes such as personal use for research, experiment, and testing for the benefit of public knowledge, personal study, private entertainment, hobby projects, amateur pursuits, or religious observance, all without any anticipated commercial application.
That means most people can't use this keyboard to write a work email or text message. That's a really restrictive license, and pretty unexpected for a keyboard, to limit what you're allowed to type. Pointing it out doesn't seem harsh.