A new blog post on the En Masse Entertainment site lays out the details and differences in the new F2P - subscription model for TERA. The game will officially introduce the new revenue model in February.
Founder status lets you keep all your character slots and bank tabs, plus you’ll receive an exclusive mount and the “Founder” title. The Terminus mount automatically shows up in your skillbook for every character—existing or new.
This applies to anyone who has supported TERA with a purchase of the game (digital or physical).