I quite like what TimescaleDB have done here - their TSL licence prohibits you from selling TimescaleDB as a service, but allows you to build new services that

I quite like what TimescaleDB have done here - their TSL licence prohibits you from selling TimescaleDB as a service, but allows you to build new services that use TimescaleDB as a backend. I'm not sure how applicable this model might be outside of databases though.