EPNS is a decentralized notification protocol that abstracts the data layer to enable sending notifications to both decentralized and centralized carriers.
Sending notifications carries a micro fee, charged in $ETH (or $DAI), the fee is controlled by the governance model.
We do know that notification needs to be carried from decentralized to centralized carriers and finally to a centralized platform which requires infrastructure and a business model to maintain it and leave the business model to the infra service building on top of the protocol.
We are running our own infrastructure ensure early adoption and to carry notifications to centralized carriers (iOS, Android, Chrome, Firefox with more to come in the future), more about this and the range of product suite is explained in EPNS Products section.
The protocol charges micro fees on notifications that are sent out. The fees from this goes to the fee pool of the protocol.