Seriously??? Aren't we overthinking this whole question? It seems, no matter the hobby forum, someone will inevitably ask this question. And it rears it's head time and time again and most likely will again (and again) in the future. Here's a thought, how about using a little common sense? Trust me, it will go a VERY long way.
If you want to make a copy of something (decals, kit part, whatever) for your own use and have the skills to do so, just do it. No need to broadcast it or ask on a hobby forum if you will go to modeler's hell for doing so. Just keep your yap shut and do it. What you do behind closed doors to better enjoy your modeling experience is your business and no one else's. Just don't make it your business to rip off other businesses by selling what you've just copied.
These mind numbing discussions are absolutely ridiculous and foolish. This only becomes an issue when you chose to make it one by posing the question in a setting such as this.
Again, can we please just exercise a little common sense and get on with modeling???
KISS - Keep It Simple Stupid