Added this to OP, let me know if there's anymore info to add regarding getting the game via fangamer.
===
You still have time to buy the $28+ tier or higher via fangamer if you wanted to get the retro game for free. (Read everything below before clicking the link)
Link:
https://fulfillment.fangamer.com/kindling/bloodstained
Once you proceed to the checkout, during the process it will ask you what versions of each game you want as in, which platform for Ritual of the Night and which platform for Curse of the Moon (retro game). Make your choices and pay, you will be emailed the confirmation of the order (check your junk mail folder), the email will confirm your choices, it will include the backer survey link if you wish to make any changes to your order.
Those that have already made their order, if you haven't made your choices in the backer survey before May 18th (time unknown), you will be given the Steam version of Curse of the Moon by default according to people in the thread here.