In their FAQ they explain making money initially by offering paid backups. What's interesting is their future plans, their vision of a cooporitive ecosystem or whatever, they make money off namespaces/domains, publishing/work contribution, in addition to the backups. This is of course if it gets engagement like notion, it will demonstrate ways to make money from an open network.

If you're betting on the tech culture moving to decentralized services this could be a way to have a foot in it.