Not a subscription but not free-to-play; rather a hybrid of these two business models. Much like ArenaNet's Guild Wars 2, you will purchase the PC game and pay no recurring subscription charges. Your purchase of the game will allow you to play in the universe for free, forever! The game will offer a variety of virtual items for purchase with in-game credits allowing you to spend money on items that offer more ways to express yourself, provide convenience, and customize your experience. But the cardinal rule regarding "in-game purchases" is: Players who spend money purchasing in-game credits will have no advantage over players who spend time!
Everything is bought with in-game credits. These purchases won't offer any advantage over someone who puts in the "game-time" to earn the same amount of credits. You might ask, why have "in-game" purchases at all? This allows us the resources to support the game on an ongoing basis as well as continually add content.