The traditional model of software licensing we all know well. The developer licenses the software to the user under conditions which usually include that the user cannot distribute or modify it, nor use any pieces of the source code for other products. Hence the code can never be put into the public domain. The result of this open source license is not only that many different people can work on the software for many different reasons, but also that the software becomes much cheaper because its impossible to produce an artificial scarcity. With the Internet as distribution mechanism this software tends to become gratis because one single freely available copy is infinitely reproducible at basically no costs.
Software needs to be clean.
Computers and software can be thought of as amplifiers. They amplify the user's agenda by giving her access to means of, say, communication that she would not have otherwise. But computers and software also amplify the agendas of their makers. For example, the realplayer allows 16 million users to listen to whatever they personally find worth listening to, the software amplifies their power to gain access to recorded sounds that are stored on-line. Effectively, the realplayer amplifies 16 million user agendas once, and one company agenda 16 million times.