> People can use those open source tools on the free level that doesn't require the higher level of use.

Fair enough.

> You're mad they're trying to make money.

I'm not mad they're trying to make money, I absolutely understand that. But again, why do they want $2.50/user from a 3rd party client, while keeping the revenue from their first party app unchanged?

The excuse for API changes was fairness (3rd party client using the API for free while making a profit isn't fair), but charging this much just shows that they don't want 3rd party clients to compete in the first place. Which is also fine, if only they admitted it.