The email in the thread below states "Complimentary parking will be available for the duration of the event." I'll add that it's an email sent to those with a resort reservation, who already get free parking, but if it was just repeating what they already get then they don't need the "for the duration of the event" part.
https://www.disboards.com/threads/moonlight-magic-epcot-link.3937385/
When we visited AK MM last year we did not stay at a DVC resort (got general registration tickets) and were not yet AP holders. However, I don't think we paid for parking - either the booths were unattended, or they just let us in. Not 100% sure, but 90%...