litellm is basically open source version https://www.litellm.ai although the openrouter being a hosted service is kinda the point. Unless the whole industry decides to this over e2ee you cant get any guarantees about an intermediary aggregator

Nobody is forcing you to use it. It’s a service for convenience: you just pay one provider instead of having to create a bazillion accounts.

If you don’t like any middle men, just go to one of the providers directly.