Hey guys. That does look to be our plugin in use there, but the frontend submission element appears to have been built by the web shop specifically. Have you checked in whether they may be able to help you? They’re at: http://summitdesignstudio.com/. (That IS definitely a solid looking calendar you linked to Filip).
Our official support for how to do this will come with the Community Events release later this month.
Looking forward for your Community Events release later this month.
Meanwhile we continue to build the total new site for http://www.hippischbelgie.be
Remember ‘later this month’ is just a few weeks away 😉