The term altcoin stems from a combination of ‘alternative’ and ‘coin’ in the sense of a cryptocurrency coin. All cryptocurrencies besides Bitcoin are referred to as altcoins in the crypto universe. Horizen’s native currency ZEN is an altcoin by that definition. Bitcoin is open-source software and anybody is free to use the code for whatever purpose he likes. Not surprisingly, the vast majority of altcoins are derived or forked from Bitcoin.