I wonder if they're successful in converting free users to paid users after they gate all useful product features behind a paywall.

I was always a light user of most products they bought and their changes just pushed me away. But as a light user, I wasn't planning to pay a subscription anyway, so going away might just release them the resources used to keep a user that generates no revenue.

However, it looks to me that the communities they buy thrive on free users. If the free users go away, will the community and usage remain? For how long will they be able to make money out of those communities until there aren't any users left?

Good question. My gut is people over value the importance of free users. Especially so if there's good business or corporate sales for the product. Free users are not zero cost on either infra or product/dev/support time.

Perhaps this is Bending Spoons real business model - understand which customers bring you revenue and pivot to product development for them not the free loaders. Sounds obvious but there aren't too many software product companies actually do it. Takes a lot of discipline as an org - generally orgs listen to the loudest voices which are most likely the ones not bringing any revenue.

Companies like Microsoft show that you can coast on a successful product for many decades and still be incredibly financially successful. And the world is a lot bigger place than selling MS Word & Excel in the 2000s.