- you say that it came from me originally
- you don't make money directly from the work
- you have at least as liberal license on your derived works (meaning that you have to share what you create as well)
Creative Commons is an attempt to create what Lessig calls a "read-write" culture, allowing specific rights for derived works. We live in much more of a mash-up kind of world. Musicians frequently use samples and other pieces of other music to create something genuinely new, not just a low-fidelity copy. The place where this is playing out in a fascinating way is in Japan, around manga (see the article entitled Japan, Ink in the November issue of Wired magazine). In Japan, there are well established serial manga stories (graphic novels) with original characters. But there is a huge market for derived works, where new (generally amateur) artists take the characters from a well known series and create new stories, frequently in directions that the original author wouldn't go (these are called dojinshi - non professional, self published manga). Imagine creating a Star Wars variant where Jar Jar Binks and C3PO ended up in a gay relationship. It is doubtful that you could sell many copies of this before a platoon of IP lawyers from LucusFilms were crawling up, well, you get the picture. Yet that's exactly what's happening with manga in Japan.
But, Japan's copyright law is about as strict as ours. Here's the interesting part: the publishers tacitly agree to allow this to continue. Why would they do this? The market for manga is huge and fickle. The dojinshi show them which series are waxing or waning in popularity. And, it provides a breeding ground for new authors. The very best of the dojinshi authors can become the next generation of legitimate manga authors. Because there is no structure in place in Japan, the publishers allow millions of dollars of dojinshi sales, with the looming threat of a lawsuit if they ever become too aggressive. The publishers are doing the smart thing: allowing a "read-write" culture which provides them lots of benefits: real-time market research based on actual sales, new authors, and a vibrant culture around their works.
Clearly, with the abilities created by digital media, copyright is going to have to change. I'm doing my part by allowing anyone to use my stuff with fewer encumbrances than copyright because I think this points to a new attitude about all kinds of intellectual property. For an eloquent presentation about this (and an incredible presentation for it's own right), check out this captured keynote by Lawrence Lessig.