The only thing you can’t do with an open API is exploit every dollar of value that passes through your service.
The main difference between a Silicon Valley API and a FOSS API, is the SV API is trying to get tons of people rich as fuck by exploiting you. The FOSS API can live long and prosper by simply asking for donations every once in a while, or engaging in very light-handed monetization.
There are like a million little nuances to this whole issue, and the lack of nuance is what Silicon Valley relies on to convince people that they must pillage their users, but that’s the gist.