Earlier quoted context omitted.
An honest question (and thank you for not using the term stealing!=)), but you listed 4 reasons. Just curious about where it crosses the line for you. If someone does A, is it still a grey area? Is it because of B? C? D? Personally, I see it as A. B, C, and D merely exasperate the situation, but without A, B, C, and D aren't an issue. Of course, the follow up is if it's because of B, C, and D that it isn't in a grey…
They're not in increasing badness. I don't think copying other people's work (a) is particularly wrong, unless you do so for profit (c). Otherwise it falls under the banner of "fair use". Taking credit for other people's work (b), even in a not-for-profit context is something I consider wrong. In combination with (c) only more-so. I think (d) is also a real issue, because it signals a certain sense of oblivious right…
I find it interesting that copying others people's work is okay with you as long as you credit them and don't do so for profit. I'm guessing it's mainly a "You know it when you see it"-porn kind of thing.
I agree with your point on D, especially as it relates to this. I think the community would be somewhat more forgiving if they'd just come right out and said "We fked up!" 37Signals did this a couple weeks ago with the cat.jpg incident.