The existing "subscription-less" application apparently will keep working until subscriptions are added in a few months time. Until then the application will work as before, so either the developer is paying the API calls or Reddit granted them a temporary exemption.
They are also not responding to questions as of whether they have a special deal for the API use as far as I've seen. Since they are neither denying nor acknowledging it, it is reasonable to believe they might have a deal and be under NDA about it.
Their announcement post is
here.