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Where does someone pay on things like Steemnova, ocdb, steemd Or steemworld?

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Steemnova is not even tied to the steem blockchain, they don't use any API at all. The others, you don't pay yet, because they have very little costs since they can use Steem as a free backend.
Steemd, Steemworld and ocdb could: Add Advertisements, Premium services or survive through tipping (donations).

Or beneficiary requirements.

Posted using Partiko Android

How do they pay for their web hosting, etc.?

There are always costs somewhere, and someone is paying them. Perhaps they are low and someone can cover them as a hobby. Perhaps (as with AWS) a free tier can allow small projects to get started without immediate payment. All of these are sensible models, but just assuming it is or should be 'free' is not a sensible model.