Open Source Blockchain
A blockchain's whole promise is trustlessness, and that promise only holds if you run a node that verifies the chain yourself instead of trusting someone's API - and if no single client implementation can become a point of failure for the network. The open source node, execution, and consensus clients here are what make that verification and client diversity possible, so the network's correctness rests on independent code rather than one vendor.
Bitcoin Core
Bitcoin node software that downloads and fully validates blocks and transactions on the peer-to-peer network
Go Ethereum (Geth)
Golang execution layer client for the Ethereum protocol with JSON-RPC access and private network support
Hyperledger Fabric
Permissioned distributed ledger framework for enterprise blockchain applications with modular components
Monero
Core Monero node daemon and command-line wallet for the private, untraceable cryptocurrency
Sui
Next-generation smart contract platform with high throughput, low latency, and Move-based asset programming
Cosmos SDK
Open-source framework for building modular Layer 1 blockchains with native interoperability
Erigon
Ethereum execution layer client with an embeddable consensus layer and fast initial sync
Lighthouse
Rust Ethereum consensus client for proof-of-stake mainnet
Stellar Core
Replicated state machine for the Stellar network that keeps a local cryptographic ledger in consensus with peers