As one of the greatest original thinkers on the planet Isaac Newton once said "If I have seen a little further it is by standing on the shoulders of Giants." Other than philosophers trying to reason from absolute core first principles (like Descartes, for example, who owned the shoulders Newton claimed to be standing upon), every creative project relies on the previous work of other people, for inspiration at a minimum and often direct imitation.

Music is an especially interesting test case, although to be certain, the pedigree of a heavily documented scientific idea is often easier to trace. So, for example, it is obvious to anyone with ears that the latest, greatest, cutting-edgiest, hip-hoppiest music is constructed around 12-bar blues phrasing, but who invented those twelve bars that led to jazz, rock-n-roll and deathmetal ambient punk? Robert Johnson? Where did he get his ideas from (well, besides the devil, of course)? More importantly, in the realm of intellectual property and copyright law, where is the line between "inspired by" and "stolen from"?

The short answer is that there is no absolute line that separates the two. Modern digital technology makes creating "original" mashups and derivative works much easier than it was in the past. This combination of fuzzy boundaries and easy instant digital copying will undoubtedly lead to a lot more theft and conflict, but I think that getting a basic grip on what is right and wrong from an ethical standpoint for yourself is important.

I'd like to emphasize that "illicit copying" is an entirely different topic from "creative borrowing," although I suspect some won't get the distinction. Fair Use doctrine covers derivative works, provided that it's "transformational" in nature. Defining "transformational" is, of course, an exercise that builds swimming pools and makes payments on the Mercedes of the copyright attorney down the street, but what I find really fascinating about all of this is that the entire concept of "originality" is a very modern invention, codified in our copyright laws (in the US Constitution, for example) and our sense of intellectual property. This raises an ironic twist to this whole discussion: Is our apparently modern concept of "original ideas" really all that original?

A fascinating lecture by Professor James Boyle of Duke Law on creative "borrowing."

In any case, inspiration is important for all creative professionals. Borrowing scenes and shots from movies you admire is an excellent way to learn, for example. Creating a shot-for-shot remake is theft (unless it's a transformational tribute of some sort). Imitating the latest effects that you see in high-end national commericials is pretty much a requirement for keeping your productions hip and fresh and up-to-date: your clients will often demand it. I think most of us have a very rough sense of right and wrong on this issue and while it's important to take this very seriously, especially if you think you might be "borrowing" too much, in the end, we should all give up the idea that anyone ever creates anything that is truly original. As the writer of Ecclesiastes wrote a couple of thousand years ago, "What has been will be again, what has been done will be done again; there is nothing new under the sun." (Ecclesiastes 1:9).

References:
* Fair Use in the Digital Age
* Beyond Authorship: Refiguring Rights in Traditional Culture and Bioknowledge
* Recent posts on originality by law professor Peter Friedman
* Copyright and the Myth of the original Creator