Considering FS is free and they are hiring, they must have some sort of monetization roadmap. My bet is either they become paid, they do paid whitelisting, or they provide some sort of sales intelligence to sellers. The first option is the best case scenario. In the latter cases, akin to Facebook, the actual customer would be sellers, charged based on the number of active users FS promises.
ReviewMeta, on the other hand, is clearly donation based, and also seems more honest at the moment (e.g., not claiming to be some sort of “trusted advisor”, showing a big warning that it’s adjusted score is only an estimation).
Monetization could be selling training data to big Amazon sellers on sentiment analysis of products. Or they just start whitelisting products, kinda like adblock does the "acceptable ads" we now have acceptable garbageproducts.
ReviewMeta, on the other hand, is clearly donation based, and also seems more honest at the moment (e.g., not claiming to be some sort of “trusted advisor”, showing a big warning that it’s adjusted score is only an estimation).