[Slippery_John]

Donations. They have a patreon and have had paypal donations long before that with the occasional donation drive to pump up numbers.

[bombcar]

Yeah they used to have a PO Box you could mail checks/etc to. I still have it in my billpay. The only gaming value that has come even close for me has been Factorio.

[Akronymus]

Maybe aurora 4x could be to your liking.