After reading them I clicked the upload button, but had neglected to check the box, and up popped a message:
You must certify that that image is not copyrighted before you upload. Please click the checkbox to certify.
After learning about copyright and license issues throught libre software this sort of thing jars with me now, so I sent a message off to the admins (after searching for ages for some sort of contact form).
Copyright is associated with a creative work, and usually is automatically assigned to the author upon its creation. This requires no special action on the part of the author, though if they are sensible they will add a copyright statement to the work to let people know when it was copyrighted and by whom. Having the copyright on a work allows you special priviledges with respect to that work.
Now just because I have the copyright on a work doesn't mean that you can't use it, but for you to do that I must have granted you a license. A license is nothing more than a statement of what you are allowed to do with the work. They can be very simple, or very complex.
Very often in the media they refer to people distributing copyrighted work when they are discussing music or film piracy. While this is true, it is not exactly the problem, the problem is that the copyright holders (the music and film companies) have distributed the work under a license that does not allow redistribution. This means that even though they have sold you the film, you can't pass it on to other people.
On the cases of CDs and films you can find the copyright statement with the familiar (C) symbol. Next time you see it read past that and look at the next bit. Usually it will say something along the lines of:
Unauthorised copying, hiring, lending, public performance and broadcasting of the record are prohibited.
Which is a license stating that you can't do much with the CD you have bought.
However it is not the most restrictive license you can have. If a work has no license attached it then it should be assumed that you shouldn't even be looking at it. This can obviously be slightly problematic.
So this means that the facebook notice above is incorrect, as what they want is not non-copyrighted material, as the copyright of most (all?) of the photos on there will be held by someone (it doesn't expire for quite some time). What they want to know is that the person uploading has permission to distribute the file on their site.
You may think that I am just being picky over terminology, but I believe that this misuse of language is actually keeping people in the dark. Whenever the media, or a website, or someone I meet talks about whether a work has copyright or not as being the deciding factor in whether it can be distributed it continues the misunderstanding. If everyone were to understand that when they create a work they have the copyright of it, and must grant a license so that it can be used by others then they may be more inclined to do so. In fact I believe that many people would grant very free licenses, massively increasing the amount of free content available.
Take Flickr for instance they provide the user with an easy way of providing their pictures under one of several good licenses. Most of the pictures I have seen on that site are provided under the more free choices.