After the Kickstarter ends, each Backer will be sent a survey to complete. In it, (among other things) they can choose either Windows or macOS for the operating system they will have their game discs compatible with, and also choose whether they will download their digital game copies from either GOG.com or Steam.
>>No need to do anything until you receive the survey.<<
This will ensure you get the discs with the games in your preferred OS. You must choose *either* PC or Mac for the discs, not *both.*
For the digital codes, your choice will be either GOG or Steam, not *both.*
Either digital retailer option allows you to download the Myst 25 games from your chosen digital retailer (GOG or Steam), and the downloads will be able to be played on either Mac or PC, depending on the operating system you're using when you log in to your account. You could play on both if you have both (but not at the same time).
The digital games will be available on GOG first, then will appear on Steam later in the year (estimated 2018). When they arrive on the digital storefronts, they will also be available for the general public to purchase.