1. Everyone gives this argument and technically, no. If you're running an Aegis server, yes. Otherwise, everything is different on eAthena, and everyone customizes their server to the point of it no longer being even close to Gravity's game. Also, Gravity makes their code open source. GRFs require extracting. Weigh the two.
2. Who cares? It's still their stuff. Not your right to take.
3. I'm not really sure what you mean by this, but if you're asking for it, that makes you the accountable thief. That means the FeelRO owner can come to you for stealing their stuff. Don't really care if you didn't ask, you're posting this on a public forum open to public opinion. If you didn't want people like me (people that run RMS, pretty much) spectating your thievery, then you should've done so in private.
5. It's anyone's business, considering, again, you posted this on an open forum.
But, I was just letting you know that by doing what you're doing, you're a thief and you're also letting the public know that you're doing it. So, if anything, I was trying to help you and your future server out considering no matter what kind of logic you try to use against the thief argument, you're still a thief and almost everyone in the Ragnarok community looks down upon it. Good luck!