What are you talking about? I’ve given you several examples of plagiarism outside of a legal concept, which means that there are non-legalistic definitions.
Here’s another one: copying someone’s homework is plagiarism. It’s not illegal, though.
I’d argue that most acts of plagiarism are actually legal, but can result in getting your title revoked. That’s not because of an IP law violation, since you don’t have ownership of an argument in an academic text.
Letting a ghostwriter write an academic paper is plagiarism, too, btw. How would that make sense in an IP law context, if the ghost writer not obtaining the IP is the whole point?
Here’s the wikipedia definition
So, I’m afraid that my definition is closer to consensus than yours.
If word gets out that you used a ghostwriter, you’re gonna get in trouble for plagiarism. That’s the thing they’ll accuse you of.
While consent is a part of why plagiarism is shitty, it’s not what makes something plagiarism. You can check it the other way around: if I’m legitimately quoting someone, do I need explicit consent, or is it implied (if it’s published work)?
About the BSD stuff: yeah, it might not be illegal and consential, but both of these things aren’t necessary for plagiarism.