Today software vendors have various ways to handle their products. In contrast to non-software products, software products' properties can be changed or controlled at a low cost; vendors do not need to extend their operations, and well-designed software can be customized systematically. Moreover, its diffusion is influenced by network externalities. The diffusion structures of software that have single user type, e.g. World Wide Web browsers, can be expressed mainly as a single reinforcing loop. This is because users can be considered as homogeneous. However, there are multiple possibilities of structure, which corresponds to business strategies for software which has divided users. An example in this category would be highly specialized software, e.g. simulation software. We attempt to explain diffusion processes and characteristics concerning network externalities of software in this category using System Dynamics models. This paper shows that multiple editions can more effectively assist diffusion of main products than strengthening network externality effects.