Who owns this?

When you submit or correct an article on the Wikipedia, you encounter the following warning:

By submitting your work you promise you wrote it yourself, or copied it from public domain resources — this does not include most web pages. DO NOT SUBMIT COPYRIGHTED WORK WITHOUT PERMISSION!

This is a very interesting statement in the context of an encyclopedia, because it raises the question of what exactly "copyrighted work" is in this context. Just where is the boundary between what I am allowed to write and what is forbidden? Let's take a look at a few examples:

1. The recipe for Wiener Schnitzel can be found in a large number of cookbooks, written by numerous authors. Does that mean that each of these recipes is copyrighted, and that therefore no two of these recipes can be identical? If I add the recipe to the Wikipedia, must I therefore invent a new Schnitzel recipe, one that has not yet been published in any of the copyrighted cookbooks? And how will I achieve this task, given that I would have to check thousands of cookbooks, and that the task of preparing a schnitzel is so simple that there isn't really much room for variation? And if anyone says, "ah, but Schnitzel is common knowledge in Austria", then I say, "okay, so spreading a Schnitzel recipe is okay, but Chicken Jalfrezi recipes are secret?"

2. Albert Einstein's formula of energy equivalency was clearly Einstein's very own and original creation/discovery. Is it therefore copyrighted? Einstein died less than 70 years ago, which would mean that the formula must not be reproduced or reprinted anywhere.

3. The wikipedia entry for Braunau am Inn contains two factual mistakes, both of which are likely copied from the Dumont Kunstreiseführer Oberösterreich, which contains exactly the same two mistakes. It also contains a number of other factoids that may or may not be copied from this guide book, but it's really hard to say, as these are historical facts about this town that may well come from other sources. But does the fact that the historical facts were already printed in a copyrighted book make them unsuitable for republication in the wikipedia, or does the fact that they are historical facts exempt them from copyright? (At any rate, the two mistakes should certainly not be in the wikipedia, not because they're wrong, but because they are clearly the guidebook author's creative products rather than fact.)

So where is the border line then? Can I copy facts from any other publication as long as I rephrase them and don't copy them verbatim? Surely not — there is the distinction between the direct (i.e. verbatim) quote and the indirect (i.e. in your own words) quote, and both strictly require the correct attribution of the source, and neither is exempt from copyright.

Simply rephrasing a different source is therefore obviously not an option. In fact, the good encyclopedias (i.e. those who list their sources of information) do indeed ask for copyright clearance for every entry that is based on a printed, referenced source.[1] But what about things that we assume to be general or common knowledge? Are they really in the public domain? Can we trust our assumption or must we expect a letter from a lawyer if we should ever decide to publish it somewhere?

Or, on the other hand, should we ever decide to write something which contains facts, does this mean that these passages can be copied from what we consider our work by anyone for whatever purpose?[2]

Does this mean that, despite the warning to not submit copyrighted work to wikipedia, current tendencies in copyright laws make it impossible to do just that? How free is what we believe to be free knowledge really, and where is the boundary between free and copyrighted? Could it really be that we are free to say what we want, but have to ask (and pay) the copyright holders whenever we want to write what we say?

[1] One of the really great deficits of Wikipedia is that, contrary to many other encyclopedias, no article lists I have not yet found a single article in it that lists the sources from which the information is taken, which would be vital for determining the reliability of the article. But this is understandable, as attributing the source could be seen as an admission that the article is not original and that it may after all be subject to copyright (although this is not necessarily the case). That is despite the fact that the information must be taken from some source — we cannot expect the Heisenberg's Uncertainty Principle to be the result of the article author's very own research.

[2] Recently, a big uproar went through the German blogosphere when a Frankfurt newspaper started printing excerpts from weblogs. It was interesting to notice how some of the most fervent critics of the copyright suddenly wanted their writing protected from being published by just about anyone — which is precisely the rationale that led to the creation of copyright laws in the first place.