The best open source software is developed by unpaid people. Even the ones with companies around them, the best work is done in the first phase when everyone is still unpaid.

The "cuts into their revenues" part usually mostly affects their ability to keep developing the non open source parts anyway, their SaaS dashboard, their billing, etc.

Take redis, you could never change it again and it's fine. There's no need to support anyone, it's complete software that stands on its own.