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.
A (maybe biased) comparison of sidechains and childchains can be found here. The main differentiation is who is securing the 'chains'. Sidechains are responsible for their own security but childchains depend on the security of the main chain.
I am not aware of any other system using the childchains approach.
As was already mentioned a sidechain implementation for Bitcoin can be found in the Elements project.
Another interesting take on sidechains is Lisk where each Dapp is implemented in each own sidechain.
In ethereum, token contracts work by initializing the total token supply to a given address, presumably the smart contract owner's address.
If a transfer is to occur a person A, the smart contract moves a given amount from the owner's address to person A's account within the smart contract itself. The gas cost is used to operate the steps in the smart contract and perform the account change.
This database in the dAPP is similar to a dictionary, but uses the ethereum blockchain to maintain previous state over time.
Ethereum tokens have all the same features as ether, but are logged a bit differently which gives them a different market value and decouples them from the ether price.