Open source software is collaboratively produced, shared freely, published transparently, and developed to be a community good rather than the property or business of a single company or person.
The major cryptocurrencies and open blockchain projects are the important examples of the open source model. All of these projects create computer networks that allow connected participants to reach agreement over shared data (the blockchain of the cryptocurrency). Developers freely fork the Bitcoin Core Github repository to either (a) build purpose-specific bitcoin-compatible applications (e.g. a wallet app for smartphones) or (b) build a new cryptocurrency that ceases to be compatible with the bitcoin network and thereby creates a new cryptocurrency network (e.g. Litecoin). Reference: https://coincenter.org/entry/what-is-open-source-and-why-is-it-important-for-cryptocurrency-and-open-blockchain-projects
