The GPL and copyright protection vs. copy protection

One interesting thing about the material on the GNU website is that much of it is copyrighted. This is a bit counter-intuitive, but it makes perfect sense. Copyrighting something doesn't mean prohibiting copying. It means laying claim to the right to set the rules for copying content and creating derivative works from that content. [I'm speaking from a US perspective here. International copyrights are a matter of international law and treaties, of which the US is a signatory]

The GPL (or "copyleft") and its descendants are a perfect example. Putting something under the GPL is not the same as putting it in the public domain. Something under the GPL can be copied freely just like something in the public domain. Unlike something in the public domain, it can only be modified and copied so long as the modified version is also under the GPL. In particular, this prohibits removing the notice that something is under the GPL (in general, something can be under copyright without carrying a notice at all). It also ensures that improvements to GPL software will be publicly available.

The basic concept of the GPL has stood up to (intense) legal scrutiny over the last twenty years and enabled the production of large quantities of useful software, including much of what I'm using to put this blog on the web. It has done so because it fits with the basic idea of copyrights, both in the literal sense of regulating the right to copy, and in the larger sense of promoting the production of useful content.

I still fondly remember the feeling of "wait ... that can't possibly work ..." followed by the gradual realization of "hey ... that might just work ..." and "wow ... this is really working ...". Definitely a neat hack.