Searching for a generally leads to two types of results: official purchase options for the commercial terminal emulator or software development resources related to other "ZOC" projects.
Unlike modern software that relies on always-online subscription checks or “freemium” accounts, ZOC uses a traditional perpetual license model. When you purchase a license for ZOC (currently version 8 or 9, as of this writing), you receive a unique —typically a string of alphanumeric characters. This key is entered directly into the application to unlock the full, unrestricted version.