[Muromec]

I imagine being part of SWIFT alliance or any other payment network costs some serious moneys, yet a current account costs a few euros a months. Same things with being a CA -- being included in the list of root certs requires an audit and obviously costs money, yet you can have free https certs from letsencrypt.

Nobody stops you from running something similar to letsencrypt but for this PEPPOL thingy if you don't want to pay for invoicing software as service.

I for once, spent 10 years of my life maintaining an opensource library so people can cryptographically sign tax documents for Ukrainian government, including e-receipts on point of sale terminals.