We all know opensource software by now and the concept behind it. If you do not like it you can change it, if you spot a but report and or even better repair it. This way the software can stay free (as in free beers) and you will create a better product every time you solve a bug.
A concept that you might not know is openbooks, you can reed some about it on the O'Reilly pages who give away some on how this works and you have the GNU Free Documentation License for example. Books under GFDL can be changed, adopted,... etc etc.. We all know also the concept of Creative Commons. All those ideas have provided a ground for a group of Polish filmmakers to create a "OpenFilm".
You will have access to all the raw material of the Valkaama project and if you do not like the compiled film as it is..... you are free to create your own movie. In my opinion this is a great concept for showing what can happen if you leave a community to decide. I will follow this closely and hope to see a lot of interesting changes to the plot.
If you are interested in the project or just want to catch a free movie, check the Valkaama project site. One of the trailers can be found below: