Are there any significant differences between these protocols? Thank you for answering.
There are many differences so I'll outline major ones. For the reference, Monax is the maker and now contributor into Burrow.
Quorum is an open source fork of a well established Ethereum client: geth. It supports and keeps unmodified vast majority of the system, including EVM and extends it to cover several additional areas:
- Pluggable consensus mechanism. Quorum ships with 3 consensus algos (Raft, Istanbul, and Clique) and theres room and interfaces for creating new ones
- Quorum enables privacy through an external side channel (private transaction managers) with proofs written on the public side of the chain
- Permissions system for creating fully private chains
Because Quorum is essentially geth client at its core, all the updates into EVM, external APIs (such as universal web3 library and the JSON-RPC standard), bug fixes, and so on are bundled into Quorum at periodic intervals.
Burrow on the other hand is a re-implementation of EVM spec around a different consensus algorithm: Tendermint. At the moment, there is no built in privacy support or permission system and it is also lacking tooling around it vs Ethereum eco-system.
Hope this helps.