Bitcoin - I want you to get it right, please! read these documents first:
https://wiki.bitcoin.com/w/Introduction -
https://bitcoinhelp.net/know/how-bitcoin-works decentralized
Bitcoin is considered the first successful decentralized peer-to-peer blockchain(ledger/database). Bitcoin does not rely on a single company or require any central services to operate. Rather it is a protocol, that people opt-in to. The consensus of Bitcoin is done by PoW, or proof-of-work which means you are rewarded proportionally to the amount of computer power you put in, compared to all others competing. To receive rewards you must mine a block, that means you create a final copy of recent transactions and sign off on it's validity. It is then propagated to all the other peers. For creating the block you receive a reward in Bitcoin which is what drives users to continue to mine. Mining now is dominated by ASIC or Application Specific Integrated Circuits. These are basically dumb computers that can perform one operation, for instance calculating guesses for Bitcoin very fast but create a barrier to entry and operations are expensive now to run. Bitcoin does not focus on smart contracts at the moment, neither is it trying to be a private chain. There are other competitors to Bitcoin, but of the ones you mentioned all are fundamentally different in their overall goals. Hyperledger, Openchain and Multichain appear to be focused on specific business use cases, and not on decentralization. They want to leverage the positives of Bitcoin without the core philosophy of decentralization. Unfortunately, it is the focus on decentralization that makes Bitcoin so appealing. A person anywhere in the world can interact with it, as long as they have internet. Private chains, and highly customized permissioned chains lock out the public and continue a standard of central ownership and central points of failure or corruption. It's up to interpretation, but open access, and decentralization are what I believe will win long term, I do not know what thing will fulfill that goal yet. Decentralization does have some draw backs. Updates are complex for everyone to agree upon, it can be slower, you can't reverse transactions or mistakes once confirmed, these often worry business and they'd rather not adjust their model for philosophy. We will see what hyperledger becomes hopefully it is focused on decentralization and not ownership of the system.
Ethereum -
https://ethereum.org/ -
https://github.com/ethereum [decentralized]
Ethereum is a decentralized cryptocurrency and smart contract network. This means the decisions to approve updates in the systems falls upon a group of users who decide to mine, re: Bitcoin mining above. Ethereum has a few primary difference between Bitcoin. It uses a different PoW or mining algorithm, which allows for GPUs (graphics cards) to participate in mining. This was intended to allow more people to compete, as GPUs are cheaper and easier to operate. It also has a smart contract language called solidity, which is code that is interpreted by the decentralized system. This means a person can create a piece of code, put it on the Ethereum Blockchain and it is possible to be interacted with or updated based on it's creation. Opening up a programming language to the masses has draw backs. It's difficult for average users to understand the code, errors can be made like any programming, and it's difficult to fix code in certain cases which can cause loss of funds or other unforeseen consequences. This is a primary reason Bitcoin has stayed away from this, as it's very difficult to get right, and for users to be safe from human or technological error. Ethereum also has it's own native currency called Ether. Ether is used a way to update state of smart contracts, and also a store of value, often used as a speculative instrument on exchanges.
Hyperledger -
https://github.com/hyperledger/hyperledger -
https://www.hyperledger.org/ [design not finalized in early stages]
Hyperledger is a collaborative project from a number of companies and organizations to form a standard framework for a Blockchain and or distributed ledger system. It is not yet fully formed. Basically they say they are working on it, but you can see on the site the number of big names who have hopped on the band wagon. The main difference is it is backed by a huge number of companies, and appears to be asserting dominance based on the groups involved. It is not yet known the full design for this system, so it's difficult to compare other than it's a movement in a similar sphere as what Bitcoin has achieved.
Openchain -
https://www.openchain.org/ -
https://docs.openchain.org/en/latest/ [not decentralized by design]
Unlike it's name, Openchain is geared towards individual organizations or groups that want to create internal chains to leverage the benefits of a distributed ledger. It would in theory be private and not a decentralized system utilizing consensus between trusted computers to perform validation. Openchain has done a lot of development and has a spec and early release. It functions primarily on the idea of dynamic permissions, allowing some entities to read/write, and others to only read/write to more public tables. Similar to any database structure where programs/users have access rights. They plan to build a more extensive framework for smart contracts which would allow specific use cases to be automated or handled with less human effort.
Multichain -
http://www.multichain.com/ -
http://www.multichain.com/developers/ [not decentralized by design]
Multichain, like Openchain is a play at a private blockchain. It is considered Bitcoin compatible, so it basically takes the benefits of the Bitcoin distributed ledger system, but makes consensus between parties centralized and/or private. Multi-chain is more developer friendly for those who have used Bitcoin before, and has less bells and whistles, so organizations would probably build upon the technology to cater to their needs, creating more of a sandbox for development, rather than an entire complete solution that openchain aims to provide.
We can only see a short distance ahead, but we can see plenty there that needs to be done.
-Alan Turing
