It has a barter system, but you don’t need to use it if you don’t want to. Nearly everything you need in the game can be harvested or made.
Their other game, Grow: Song of the Evertree, is pretty fun too. It’s partly a city builder, partly exploring new worlds that you create. It’s been a while since I played it, so I remember some sort of currency, but I don’t really remember having to work that hard for it. Mostly, I just focused on creating worlds with crazy elements.