Nostr is like a decentralized message queue/database with cryptographic identities. It has been funded by Jack Dorsey. Its most common usages are a decentralized Twitter clone, a tailscale clone without any registration needed called NostrVPN, and diVine, a revival of the classic Vine service. But there's also very interesting stuff like this, a completely decentralized git that uses public relays and cryptographic identities to control ownership.