GNUnet

GNUnet is a software framework for decentralized, peer-to-peer networking. It provides the underlying structure for networking software in which participating systems operate as peers, rather than depending on a centralized system. It can be used to build and support decentralized network applications, including software in the messaging category. GNUnet is intended for developers and projects that want to create peer-to-peer applications without designing their networking foundation entirely from scratch. It is not presented as a replacement for a specific paid product. An important limitation for people seeking a ready-to-use messaging service is that GNUnet is a framework, not a complete end-user messaging application. Developers must use its structure as the basis for the decentralized network software they build and support.