Because Redis said they would never do something and then changed their mind (which makes the whole concept of saying you will never do something useless), while Amazon never said they wouldn’t use open source software for free (which is their right).

I'd still trust more antirez than amazon as entities.

Never trust a company.

What does trusting antirez help me if he’s working for another company?

You're not arguing for the honesty of individual companies, you're arguing against the profit mechanism.