It is remarkable to think that even without any interest in finding suitable methods and concepts that would allow complex software systems to evolve and remain manageable, the ever growing open source movement has silently managed to establish highly successful evolution techniques over the last two decades. These concepts represent best practices that could be applied equally to a number of today?s most crucial problems concerning the evolution of complex commercial software systems. In this paper, the authors state and explain some of these principles from the perspective of experienced open source developers, and give the rationale as to why the highly dynamic "free software development process", as a whole, is entangled with constantly growing code bases and changing project sizes, and how it deals with these successfully.