Philosophy rules the dilemma
The question of exclusive and inclusiveness of these platforms doesn't necessarliy determine the useability of one over another. I think its matter of culture, philosophy and business need of any organization that literally determines the platform. More specifically, the operation costs of IS system and the size of company plays a key role in implementing the COTS or Open-source platform. Also, the need of research and development, the availability of open-source enthusiasts, the availability of infrastructures and the business need are the key-factors. However, it is non-deniable that for the majority of these issues, open-source easily supercede the proprietayr platform except in the support and operations. Nevertheless, if you have a good operation along with research and development-team, the open-source is unbeatable.