CJDNS is a self-organising IP address allocation and routing layer. A node's public key acts as its IPv6 address, and routing uses a DHT of those nodes.
This style of network has the property that you can take two independent CJDNS networks, link them together, and all nodes are mutually addressable/routable. This is in contrast to The Internet, whose addressing is centralised on IANA.
cjdns is moderately active, though most links between nodes are via an overlay on top of the public Internet. The goal is to have physical/wireless links between geographically close nodes.
Use https://peers.fc00.io/ to find a cjdns node geographically close to you.
Decentralized protocols such as ipfs/scuttlebutt work particularly well on cjdns, as a file shared on ipfs in one network, will automagically become available on another network, once those networks are linked.