Output licensing is not uniform and not intuitive. Some models permit unrestricted commercial use, some restrict it by company size or revenue, some restrict specific sectors, and some change terms between versions of the same product.
The check happens before rendering, for the specific model and version being run, and the answer gets written into the consent file. Discovering a restriction after delivery is discovering it too late to do anything except stop running the campaign.
Open weights are not the same as an open licence. A model you can download may still carry usage restrictions, and the two questions need answering separately.
Does an open-weights model mean unrestricted commercial use?
No. Availability of weights and the licence governing output are separate questions, and plenty of downloadable models carry real usage restrictions.
When should licensing be checked?
Before rendering, for the exact model and version in use, with the answer recorded. Terms can differ between versions of the same product.