Free? That's wishful thinking as it will be a chargeable service due to a £243m bill to pay off plus interest and operational costs. The service will not be run by the airport operator but by the Council via LLAL who will subcontract the operation to a third party via a tender. It could well end up being the UK's most expensive 1 mile journey with penalty charges for fare dodgers. I don't know if it has been granted yet but the Council has applied for a Transport and Works Act Order. The application will provide powers relating to the operation of the passenger transit system linking Luton Airport Parkway Station and the Central Terminal at London Luton Airport.
https://dart.llal.org.uk/wp-content/...t-May-2020.pdf
The more passengers that use the Dart the less the airport operator makes in drop off and car park fees, which they keep as part of the concession agreement with the Council. This might partially explain why despite their cheesy smiles about the Dart why they refused to put a penny towards it.
I am still not sure whether there has been an agreement made for the rail operators to sell a single ticket solution to the airport. I think the best LLAL can hope for is a 2 ticket solution but one fare paid at the railway station otherwise the Dart operator will be responsible for collecting rail tickets. The worst option is that tickets will have to be bought at the Dart stations for the Dart train.
There are plans for Parkway to be made an Oyster Card station but so far no agreement has been reached. Whether that could be extended to include the Dart is another question.