Unethical for whom?
(Scroll to the end to find my stance.)
That would be my first question. For a die-hard follower of libre software ideology, personal use of a proprietary software could be unethical for them. But they may also extend their definition of ethics on others, arguing that if a user willingly chooses to use a proprietary software than they lack ethics.1
We collectively prohibit questions on blatant piracy not only because piracy of a software stands illegal in many jurisdictions but because there is enough agreement elsewhere that it amounts to theft which jurisdictions and many individuals (barring pirates of course) finds unacceptable. Furthermore, piracy doesn't lead to innovation/betterment in/of the product, neither does it, primarily, gives any insight, technical or otherwise, in the software. It further would cause legal ramifications for our site, so we steer clear from it.
The date-time issue in the linked question is a flaw in the app (no matter if it is prevalent in various apps) and the OP intends to use that for personal gains. Leaving aside any violation of intellectual property (IP) of the developer, I think OP's actions amount to theft if the software is a paid one. For me, that is an unethical practice and I would not support it if the motives are clear or the app or its features has to be bought.
But, what if the app was free for use forever? What if OP decided to see the behavior of the app when the date-time or something else is tweaked? What if the app couldn't handle this and force-stops or produces garbage output on screen? There involves plain and simple curiosity at their side. But, though no theft of potential money is involved, there may be a violation of somebody's IP.
Consider SHAREit as an example. Assume that you don't like the shipped user profile icons set and wants to add more into it. Say SHAREit does not offer one, neither would it in the near future. Now, you decided to take things in your hands. You found that you need not to disassemble its APK to add more images since the data directory of the app has them at a dedicated location. You just added more of your icons there, restarted the app, and voila! objective completed.2
But, SHAREit's Terms of Service (TOS) notes:
You will not, nor allow third parties on Your behalf (i) to resell or charge others for use of the Application (ii) to duplicate, disassemble, decompile, transfer, exchange or translate the Application, create derivative works of the Application of any kind whatsoever or attempt to reverse engineer, alter or modify any part of the Application
They say that TOS is binding legal agreement subjected to jurisdiction of courts in Beijing. Now, if you're outside the Chinese jurisdiction, you may not consider the modifications illegal because you as a sovereign would be subjected to only those laws your State has ratified or promulgated. However, what about ethics?
- Are you not violating a contract that you have with somebody?
- Did you take their consent to modify the app for your purposes, even if non-commerical they may be?
There is definitely a clear violation of IP which hurts their interests over yours.
So I leave this to you to ponder about: just because there is not a paid product involved, do you find the modification ethical at the cost of IP? Did you consider that IP finds its place and protection in Universal Declaration of Human Rights.
Now, as a member of the community, where do I stand than?
- If I'm convinced that product or its features has to be paid for, I would downvote and close vote because I don't want the developers to suffer monetarily at the cost of my curiosity or of asker's. If there is an answer, I would flag it for moderator intervention. Their judgement would stand final of course.
If the product is free for use, then I consider case-by-case approach. My very limited experience tells me that developers (Corp./Org./Companies,etc.) often do not legally chase away just anyone any time. When there is considerable damage to them, say brand image being tarnished, or product used for anti-social/anti-national/illicit activities, or monetary damage of some kind, or some alike cases, only then they come into action.
It is when any of this has been established I consider it unethical for myself to support app's modifications publically through knowledge dissemination. However, I don't find it unethical to modify the app if the knowledge to do so remains with me or when I'm unaware of the aforesaid developments taking place.
The reason I use case-by-case approach is because I cannot trade my curiosity for somebody's IP every time. Curiosity is my driving force to hang around on this site and post working answers and gain satisfaction and ultimately, end up helping people along the way.
1: I'm neither supporting free software ideology nor opposing the use of proprietary software.
2: This is purely hypothetical. No violation of TOS took place for this answer.