They use Clarifai
Source: https://www.clarifai.com/
> In order to connect brands with the images they’re looking for, Foap uses Clarifai to consistently tag all these photos to make them easily searchable.
Pricing: https://www.clarifai.com/pricing
More on Foap <-> Clarifai: http://blog.clarifai.com/uncover-buried-stock-photography-tr...