No, Council members are not required to build applications on the Hedera network.  Companies are generally seeking to join the Council because it provides them with a leading role in the management and development of what could become a transformative technology. Council membership will allow them to have a front-row seat in understanding advanced distributed ledger technology and use cases. There is no requirement for Council members to use Hedera network services. We would note, though, that all Council members to-date have expressed an interest in exploring the development of distributed applications on the Hedera network.