Everyone! No single person or organization owns the network. The network instead is run by all of the users around the world. Developers improve the software, but they cannot force a change in the protocol due to the fact that all users are free to choose what software they use. Every software developer has to keep in mind the issue of compatibility with the network, so developers tend to follow established rules to ensure a wide adoption. Consensus is key and therefore all users and developers must agree and protect the direction of the software.