Hashgraph is a distributed ledger technology that has been described as an alternative to blockchains. The hashgraph technology is currently patented, is used by the public ledger Hedera, and there is a grant to implement the patent as a result of the Apache 2.0's Grant of Patent License (provision #3) so long as the implementation conforms to the terms of the Apache license. The native cryptocurrency of the Hedera Hashgraph system is HBAR.
Unlike blockchains, hashgraphs do not bundle data into blocks or use miners to validate transactions. Instead, hashgraphs use a "gossip about gossip" protocol...