Thread on reddit by the head of TheTVDB himself:
TL;DR 12 US$ per year for having access to TheTVDB API to scrape info for your TV shows and movies in the future. They might introduce an additional plan which lets you earn credits if you contribute data to the site.
Just a heads-up for fellow Kodi users. Although I like(d) the site and contributed a pic here and there, and some info on actors and such, I think this is the coffin nail for the endless problems with TheTVDB. Now’s your chance to familiarise yourself with creating .nfo files or look around for alternatives like TVmaze.