What Underlying Framework Is Used for BCS?

BCS uses the Hyperledger open-source framework.

Hyperledger is a blockchain open-source project hosted by the Linux Foundation to establish an underlying architecture for the distributed ledger platform oriented to multiple application scenarios. Hyperledger has sub-projects including Hyperledger Fabric, the most important one, and many other related projects derived on top of it. Developers from various sectors, such as finance, banking, IoT, supply chain, and manufacturing, have contributed towards this project seeking to build cross-field blockchain applications.