This isn't true. Modules are free (unless you're a hosting competitor) so there is no licensing revenue there. They might be charging a handful of enterprise customers for special module support, but that isn't their main revenue stream. Their revenue is from Redis Enterprise which is a Redis hosting solution (managed cloud, unmanaged cloud or on-prem). Redis Enterprise is entirely closed-source, but it's an infrastructure management system and not a data store (it isn't Redis).