Hyperledger.
This is an umbrella project which includes several platforms. The developer is a non-commercial organization Linux Foundation together with IBM, Intel etc. There are five blockchain projects:
- Fabric
This project is right now the only one that is production ready. This private blockchain is promoted by IBM. It has the division of rights, Kafka consensus algorithm, interesting architecture and smart contract based on Golang and JS. It has modular architecture and the functional areas are separated into different layers, nodes have various roles. There are different nodes responsible for the consensus and code execution and data operations. Fabric is supposed to be an intermediate tool for the already existing infrastructures. SDK can be used for user interaction. As for the speed the data ranges from 300 tps to 3500 tps in theory. - Iroha
The project is very similar to Fabric and is promoted by Soramitsu. It uses the BFT consensus library Sumeragi, smart contracts are based on Java, the project is oriented on a mobile usage and small data volumes. - Sawtooth
The platform is promoted by Intel. It is using a lottery algorithm Proof-of-Elapsed-Time and works with an Ethereum VM from Burrow project. Solidity is the main language used for the smart contracts. Intel announced that the platform would be ready for industrial uses in the beginning of 2018 so we still lack the data on the real cases and the speed. It is supposed that Etherium VM will make the design process easier and the lottery consensus algorithm enhances the opportunities for scaling. - Burrow
It is the joint project of Monax and Intel. It is supposed to be using the virtual machine partly corresponding to Ethereum with division of access rights and modular client. Burrow was approved for incubation. - Indy
The platform is developed by Sovrin Foundation for decentralized work with identity-information. It has Phenum, its own RBFT protocol implementation.
Neo
The idea behind the platform is to create а better solution to substitute Ethereum basing on the Chinese market. It uses dPoS-consensus, its own virtual machine and smart contracts written in the popular languages such as Java, C#, Python etc. Though the number of projects is not high and development has its difficulties. As for technology itself there are also some issues especially because of the lack of decentralization and usage of dPoS-consensus in a public blockchain.
Waves
Waves is a Russian open source platform for derivatives exchange. It is quite similar to BitShares including the very limited smart contracts. The platform uses its own version of dPoS-consensus – Leased-Proof-Of-Stake. The Turing complete smart contracts are expected in 2018 Q4.
Stellar
This is a system oriented on the fast and cheap exchange of digital assets. The system is good enough for simple automation tasks using API, also possible to use for the ICO. Though still some research is needed in case of complex decentralized applications. Stellar utilizes advanced protocols of FBA, Federated Byzantine Agreement which is an improved version of the one used in Ripple.
In summary: if today I needed to choose an Ethereum alternative for some abstract project, let’s say, an MVP Dapp, I would try NEM. If I needed something for a one-year period, I would prefer Cardano. And for some simple scenarios, e.g. ICO, Stellar would work. But this is just a technical approach and economy together with marketing can influence the choice of a platform.