Sure, but frankly it's historically very hard to build a business around a specialized database, especially if you have competitors that are even 80% as good but free.
The cases where I've seen this work are when the DB offers something way ahead of what their competitors offer. For example, KDB+ was historically unrivaled when it came to ultra high performance time series storage and Aerospike is very hard to beat for extremely high performance multi-node K/V.
Otherwise there's little to stop a larger company from offering the OSS competitor to your DB as a service for a lower cost and invest eng resources to close the gap.
The cases where I've seen this work are when the DB offers something way ahead of what their competitors offer. For example, KDB+ was historically unrivaled when it came to ultra high performance time series storage and Aerospike is very hard to beat for extremely high performance multi-node K/V.
Otherwise there's little to stop a larger company from offering the OSS competitor to your DB as a service for a lower cost and invest eng resources to close the gap.