Is Medieval Booker free?
Medieval Booker is free to use: every festival page, country and month listing, and article on medievalbooker.com is open to everyone, with no account and no paywall.
Medieval Booker Knight is an optional paid membership that costs $4.99 per month, or $49 per year (US dollars, tax included), billed through Polar, and you can cancel at any time. The first month is free. Knight is a paid membership, not a paywall: members follow the festivals they care about and see every change to their dates on their account, and receive one letter a week with a piece of medieval history, a festival guide and places to visit in Europe's old towns, all kept in a library on their account.
That membership is how the hours spent emailing organisers get paid for. Display ads may one day pay for the servers; if they arrive, they will be labelled. Listings are free for festivals and always will be: nobody can pay to be listed, ranked or recommended, in the site or in the letter, and there are no affiliate links in any festival's facts. If that ever changes (a labelled "where to stay" box, say), it will say so on the page.