For not depending on altruistic action, I like the opencollective model. Both for self financing but as a platform too. If you use their platform to provide paid services, you share revenue for development. And then development/processing is charged from the collective fund through open recipes.

I expect most drivers to already be legal drivers. And the main point is to empower organisations that are already in place. Legally, I suppose the difference is that this is actually a technology project, with technology goals? The legal responsibility would be of actual operators.

Drivers drive as a job. Fees defined by the operator. Processing through payment modules. I was thinking each would need their own stripe API keys, for example. Split is also defined by the platform.

Trust would be built through moderation and finance. Operators can make some screening of customers and drivers, to increase trust between both groups.

I expect operators to provide support for any problems, since they choose the drivers explicitly. Including refunds. They got full control over finance.

If anything worse happens, I'd expect the operators to be in the hook. This is their service, actually. They have finance, they have actual full control.

If someone makes online stores with WordPress and doesn't delivery their goods, or deliver harmful goods, I don't imagine WordPress can be held accountable.