The authors reside in a country which is known for its rampant violations and theft of intellectual property.
Is it equally unethical to reverse engineer their modified software and release it as open source? Two wrongs don't make a right etc.
You're not "stealing" source code, you're deducing operational concepts and then reimplementing it with your own work. That's perfectly fine in a lot of, if not most cases.
(Legal exceptions: your country forbids reverse engineering, or the software is patented [= in both cases, your legal system sucks]. But those are legal arguments, not moral.)
In other words ethics are whatever you say they are. And polling the internet for permission will turn up a mix of aye and nay.
Is it -legal-? That's a different question, and "ethical " questions are usually a prelude to breaking some law under the implication that the law is "unjust".
As an aside I presume you are a -customer- of said company? Since GPL rights only applies to those with a legal, binary, copy.
Morality tends to be an implementation of ethics, like respecting the dead by leaving them to be eaten by vultures, or burying them instead.
> Ethics are more universal
Both of these statements will have philosophers up in arms ;D
Whether morals (and transitively ethics) are universal or context dependent is an unanswered (and possibly undecidable) problem in philosophy. https://en.wikipedia.org/wiki/Moral_universalism - https://en.wikipedia.org/wiki/Moral_relativism - https://en.wikipedia.org/wiki/Moral_nihilism
The authors have (allegedly, and according to you) committed a GPL violation.
The "sins" of the country they live in have nothing to do with the situation.
Reverse engineering closed-source software is generally legal, as I understand it, unless the software is patented, in which case, it isn't. If the software is patented, I'd lead towards it being unethical to break a law in your jurisdiction because you (not through a legal system) have unilaterally decided that they committed a violation.
“Hacking” the proprietary code is no different than if there had been no GPL violation, under the law.
Looking at the inputs and outputs and guessing the implementation is legal, but I guess the OP meand decompiling the executable and using the decompiled source that is ilegal.