All coding clubs (Dojos) are absolutely free to attend! This is an important aspect of the CoderDojo ethos: CoderDojo places a strong emphasis on free open-source learning and sharing of knowledge in order to provide young people all over the world with equal opportunities to learn about code and digital making, regardless of their financial circumstances. Young people and their parents/guardians should never have to pay to attend a Dojo. This is ingrained in our ethos and our Charter of Ethics: http://kata.coderdojo.com/wiki/CoderDojo_Charter_of_Ethics
While Dojos are free to attend, most Dojos use a ticketing system, e.g. the one on our community platform Zen or on a trusted third-party website such as Eventbrite, to keep track of sign-ups. Tickets should always be marked as free, and attendees should never be asked to enter any personal payment details. Ticketing is used simply so that champions can manage the number of attendees.
CoderDojo is a volunteer-led movement in which Dojos are set up and run by volunteers. Occasionally, Dojo organisers may accept voluntary donations or hold fundraising events in order to cover some unavoidable costs of running a Dojo, such as for equipment etc. Dojos may have a discreet donation box at their sessions, but attendees/parents/guardians must not be made to feel like they have to contribute.