I didn't see anything about it being free. I also didn't pick up on whether or not it was moving behind a paywall, just that you could buy a vip subscription for 20% off
I think in the email they sent out they mentioned that each IP would be able to download 5 per 24 hours and "registered users" 10 per 24 hours. Paid members would be restricted to 1,000 per 24 hours.
It's 15 bucks a year for VIP, if I understood it correctly, then I am of the opinion there is nothing here to get mad about for "regular users".
Your consumer can query the API on its own, and download 5 subtitles per IP's per 24 hours, but a user must be authenticated to download more. Users will then be able to download as many subtitles as their ranks allows, from 10 as simple signed up user, to 1000 for VIP user.