Are there any other blockchains that can spawn child-chains within their own blockchain like NXT's Ardor platform? NXT is transitioning into a child-chain or sidechain type of blockchain as a service model. I know Bitcoin has the ability to issue colored coins on counterparty and colorcoins, but is there something similar to what NXT's Ardor platform is doing? Where by you can copy the existing blockchain features, but spawn your own while using the parent chain to secure it. Is there development going into this child-chain / side-chain arena in either Bitcoin or another Altcoin?
With special transactions, Bitcoin has the capability of supporting sidechains. This is different from childchains in that the sidechain itself is a different blockchain and is not extended from the main blockchain. The paper describing sidechains can be found here: https://blockstream.com/technology/sidechains.pdf and an implementation of those sidechains can be found here: https://github.com/ElementsProject/elements.