Is Red Hat Proxy subscription sufficient for Red Hat Proxy installation & registration?

Issue

1. Is it mandatory to have valid Red Hat Enterprise Linux subscription and Red Hat Network Proxy subscription for RHN Proxy server? Or just need to have Red Hat Network Proxy subscription to build and configure RHN Proxy server?
2. Clients which are registered with RHN proxy server, do they need valid Red Hat subscription for them or only RHN Proxy server license would be enough? Is valid subscription required for each client apart from RHN proxy server license?