Richard Fairhurst has an excellent post on this subject in the context of cartography. I don’t agree with his conclusions, though:
The Red Hat model works well for people who can be employed as technicians. During the day, you get paid for supporting Linux; you go home, under the roof paid for by your day job, and hack on the kernel during your free time. That’s great. That doesn’t work for art. If you want to earn a living from art, you can either become a gun for hire – working to patrons’ commissions – or you can have the brave faith in your own abilities that, some day, someone will pay for the art that you are compelled to make. Either way, you can only keep up with the mortgage so long as people are prepared to give money to own, or use, your artistic creation. There is no equivalent of the Red Hat technician.
In fact most artists (musicians, painters, sculptors, writers, poets, etc.) are exactly the equivalent of the Red Hat technician. They make money from residencies, competitions, technician jobs, evening classes, lecturing, readings, performances, tutoring, commissions, and other payment for services. Just making and selling art doesn’t pay the mortgage until you have a reputation or an audience. To get paid until then, and to build your reputation and audience, you need exposure. Copyleft helps you to get this, and it keeps that work for you later.
For autographic art (painting and sculpture), there is always the original object to sell. For allographic art (music, literature), there is always performances and deluxe signed editions. There isn’t getting rich from selling reproductions (unless you sell them yourself; if bottled water can compete with free there’s no reason why art shouldn’t), but then very few actual artists get rich from reproductions. CDs and paperbacks make lawyers and executives rich, rarely the artists. So artists either get paid using the Red Hat model, or use that model to become Red Hat executives, er, well-known artists.
The problem that Richard identifies of artisan cartographers not being able to pay their mortgages because people can copy their BY-SA maps if they are derived from Open Streetmap data (a scenario I’m not sure will work given the copyright status of map data) is solved by the details of how the Red Hat model works. Artisan cartographers commissioned to make maps are paid by the third parties that commission and print the maps. People will photocopy small maps anyway, and will not take the time to copy large maps. In these circumstances the only problem is that BY-SA may put the map commisioners off, but this assumes that they dislike freedom (and don’t think its network effects will protect them from competition) more than they dislike paying for data from the Ordinance Survey or elsewhere.