[dividuum]

> With ByzCoin, if you can't reach quorum, you can't make progress [...]

This may be a stupid questions, but how does such a system prevent me from adding new nodes, only to remove them all at once if I want to prevent the system from progressing?

[bascule]

The participants in the consensus group are selected via PoW. You would need to control > 1/3rd of them (i.e. 1/3rd of the nodes that have recently won the PoW leader election race/lottery) to cause Byzantine faults.