I found a really interesting blog about copying/plagiarism vs. inspiration: You Thought We Wouldn't Notice. It's helping to fill in one of the gaps left in my education at PSU.
I came up through the anthropology program at U of O with a very strict outlook on plagiarism in academic writing. Basically, if they thought you were copying someone else's work, you would wind up in deep shite indeed. Even improper citation could land you in trouble. I was pretty much death on the subject of plagiarism, so in anything I wrote, I was incredibly careful to properly cite the source for any idea that was not my own.
In PSU's art department, things were very, very different. While they do not, in any way, encourage direct plagiarism, students are occasionally encouraged to "copy" for inspiration. I'm still very confused about the differences between artistic plagiarism vs. homage vs. inspiration, but reading through You Thought We Wouldn't Notice has been helpful in starting to sort things out. There are still a lot of gray areas, though.
For example, I've been looking at a lot of vintage illustrations lately for inspiration:
The image on the left is a vintage magazine cover that I used as inspiration for my drawing on the right. Comparing the two side by side, the inspiration is obvious. However, an artist friend told me that I'd reached the "changed enough" threshold for my work to be creative, rather than completely unoriginal. Should I end up selling this drawing, I would add the information about what inspired it. And that seems to just about safely cover the ethical bases for creating a derivative work.
Nonetheless, I'm still a little worried. I'm working to develop my skills as an illustrator and further develop my own creative voice, but part of that is being deeply inspired by vintage imagery and visual conventions. I'm basically an honest person, and want to make sure I stay within the spirit of ethical boundaries, not just the letter. I had a lot of fun creating this particular drawing, and I think my own visual voice comes through. As I go along, I hope to hone my sense of where the line is, and maintain my ability to stay far to the right side of it.
(Sorry about the poor image quality, I'm hoping Santa brings me a scanner for Christmas.)