While it hasn't been properly publicly announced yet, GOG Patrons is a new system launched by GOG to hopefully pull in more people to donate. This isn't the first time GOG have asked for people to donate, as back in June they added a donation form to the checkout page but this goes one step further.

The main point of the GOG Patrons program appears to be directly supporting their game preservations efforts as part of the official GOG Preservation Program. Not to paywall anything on the GOG store, just as an additional way to support GOG directly.