Is Open-Source -film production possible with open-source tools?
The production group you refer to has a team of 20 guys ("no girls") and 40 computers. Do you think there is an open source for 20 CGI professionals and 40 computers too? This is a very real production company with a budget to get things done. They have created enough attention to fund the project 'Iron Sky'. No easy task.

What you are asking is like this, you see a beautiful Lamborghini Murciélago and want to know if you can make one of these with free tools and labor. By the way, what you are asking costs way more than a Lamborghini Murciélago. I would say that you have a very ambitious mind. However, there are no free open source tools that can do all the things these guys are doing and I would include the skilled labor of these 20 guys and the cost of 40 64 bit i7 machines as well.

Even if it were possible to replace all this great software with a free open-source version, where are you going to get 20 skilled and seasoned artists with 40 computers to do this work for you? I can't stress the importance of who the people are that run the programs and make the editing decisions. Software will come and go, but the imagination and talent of a skilled team is priceless and timeless.