There is a respectable amount of freedom included in the game. With regards to NPC interaction, it can range from idle chat, trading, quest requests, first-aid help, inquiries on recruiting members to your community, and the like.
Not a people person? Well you can always go the hostile route if you wish, rob anyone you meet or even outright murder them for no reason. You can even force them into labor at your community if you intimidate them enough.