As a matter of fact, Pythagoras was very important for the further development of mathematics - exactly because it was free and stimulated others do build on it's foundations. The same applies for software, which consist of ideas and the actual implementation of those ideas in computer language, often called "code". The implemantation, the code, is protected with copyright. That means that you can freely implement and improve any idea, but you have to provide for your own implementation. Otherwise, the effort and investment of others would be hurted. The ideas flow freely, so that the competition on the implementational level may be even harder. One company implements the idea of a word processor in a way that attracts many people, while another company tries to attract students. Competition is good and drives innovation. One can observe this in the open source world, where competition is often heated.
Now enter the world of patents. We start to limit the ideas. If some company, usually a big one, patents an idea, other companies are no longer able to use that idea without a penalty. For example, image a hyperlink. Each time you click on a search result, you use a hyperlink. If that was patented (it nearly was), then such technology would be restricted. Of course, the new European Patent Organization would not patent such existing and widely avaiable technology. Or would it? Not very long ago, the hyperlink was a revolutionary idea. Now it is used everywhere. That is the way innovation in Information Technology works: the revolution of today will be the foundations of tomorrow's innovations. A typical small computer program typically involves thousands of such revolutionary ideas of the past. By restricting these new ideas, and only allow the "inventors" of the ideas to implement it, innovation will be slowed down.
Patents will protect big companies, who have enough staff and many to scare away smaller companies with patent wars. The big companies know thet violate each other's patents, which is unavoidable, but resorts to gentleman's agreements. The smaller companies and the open source movement have no defence againt them because they do not have the means to make such gentleman's agreements. Even governments who like to use open source are likely to suffer, and will become more dependant on big companies.
The open source movement will be forced to hide and seek freedom in encrypted storage, communication, and private networks. Already, completely private information sharing is possible with systems like Freenet. Such systems and tools will be improved and their popularity will grow. Such technologies are very useful for music pirating and other illegal activities. To drive honest open source programmers to private techonogies means to stimulate the development of software which can be used in less legal ways.
The question remains: why software patents? Obviously, the big companies have made up a good story. But software patents don't add much to the already existing copyright restrictions. They limit the widespread implementation of new ideas. They threatens small companies, governments and open source. And pirating will be stimulated.
About the author:
Evert Mouw is a certified Microsoft professional (MCSE) and an enthusiast Linux user. He administers a small company network and studies political sciences in The Hague, Netherlands. He wrote an GPS add-in for Microsoft Mappoint and maintains a Dutch website with information about fighting spam. His email address is post at evert dot net.