The first and most profound misunderstandig people can have about Wikipedia comes from its subtitle: the free encyclopedia.
‘Free’ can mean practically everything. Joachim Gauck, the 2010 presidential candidate in Germany, speaks about the ‘freedom concept of the pubescent’ when someone believes that freedom means ‘I can do anything I want’. In fact, we frequently meet people who complain that ‘their’ article has been deleted, and they wonder how that can happen in a ‘free’ encyclopedia.
In Wikipedia, ‘free’ relates to the concept of ‘free content‘, coming from the movement for ‘free and open source software’. Sometimes it is presented as an alternative to copyright; seen from the more European concept of Urheberrecht (rights of the author), it is more of an option. The author can allow that his work can be copied, spread and altered, and as it is the wish of the author, the courts take ‘free content’ serious.
In ancient times and the middle ages, immaterial rights where largely unknown. Someone could possess a book, and it was a crime to steal that book, but usually nobody cared if another one copied the book. Especially in the case of an encyclopedia, the writers saw themselves as sedulous bees, as craftsmen and compilers, passing old and proven book knowledge to the next generations. 
Some essential things changed during the late middle ages and beyond. Knowledge could become dated because of experiments; the quantity of knowledge exploded and needed reduction to comprehensive summaries; authors claimed originality and were no longer too modest to publish under their own name. And, even it took a long time, the production of books became cheaper. In the middle ages, an encyclopedia existed usually in some hundred (hand written) copies, in the 18th century it were some thousand copies, and after that ten thousands or even more.
In the 19th century, it was no longer possible to write an encyclopedia by pure plagiarism, also thanks to modern copyright. Texts and pictures became ‘unfree’, as some of the activists for ‘free content’ might say. Information itself remained much more difficult to ‘protect’, everyone is free to say that Mount Everest is 8848 meters high and that Buenos Aires has 2.7 million inhabitants.
Also for Wikipedians it is difficult to tell exactly what they are allowed and what not, or what is suitable to do. There are texts and pictures that became free because of old age, for example previous editions of Britannica and Meyer. The English and German language Wikipedians were not always enthusiast about e.g. Britannica articles of 1911 – it took a lot of time to make them a little bit up to date.
In summer 2009, the case of the London National Portrait Gallery (NPG) was hotly discussed. An American Wikipedian, Derrick Coetzee, took for about 3,300 pictures from the NPG’s website and uploaded them to Wikimedia Commons. The pictures were free because their age, but NPG complained at Wikimedia Foundation. NPG had paid more than a million pound to scan the pictures and wanted to make money with high-resolution versions (the pictures on the website were presented originally in a way that made downloading and copying difficult). In Britain it is possible that a database is protected by copyright, NPG said, but WMF answered that the comparison to a database does not work.
One year later, Wikipedian Liam Wyatt asked on his blog: ‘ Who would you least expect to attend GLAMWIKI-UK?’ Indeed: the head of rights & reproductions at the National Portrait Gallery, Mr. Tom Morgan. After Mr. Morgans presentation ‘Wikipedia and the National Portrait Gallery – A bad first date?’, Liam Wyatt had a nice conversation with him. Their disagreement on some legal principles remained, but Liam Wyatt described the atmosphere with a quote from a tv show: ‘You can happily question our methods, we do that all the time, but don’t question our motives’.
 Robert Luff: Wissensvermittlung im europäischen Mittelalter. ‘Imago mundi’-Werke und ihre Prologe. Max Niemeyer Verlag, Tübingen 1999, p. 414.