Hive is a dApp. Koinos is a dApp platform. In short, smart contracts. Hive is a specific suite of smart contracts (a dApp) that is mated to a decentralized network that is extremely difficult to upgrade and which developers cannot use to run custom code (smart contracts). By migrating some or all of Hive to Koinos, the Hive dApp developers will be able to retain the fee-less nature of the application, eliminate the need to hardfork, and gain from our scalability solutions.