The Invisible Internet Project (I2P) is a garlic routing using overlay network and darknet that allows applications to send messages to each other pseudonymously and securely. Uses include anonymous Web surfing, chatting, blogging and file transfers. The software that implements this layer is called an I2P router and a computer running I2P is called an I2P node.
License: Open Source
I2P provides strong anonymity for users through its onion routing method, mainly focusing on hidden services, whereas cjdns creates a decentralized mesh network that allows more general internet access but with less focus on anonymity. Both projects have their unique strengths and weaknesses, catering to different user needs.