Salem is a fully open sandbox MMO with deep crafting elements. The game features permadeath as one of its main ingredients, along with an in-depth character development system without set roles, where the player can chose which kind of game to play. Taking place in the time of the first Pilgrims, Salem lets you live as an explorer in the new world; building your settlement, learning new skills and maybe fight with your neighbours.
The only place in Salem not built by the players is the main city Providence, which is a safe-zone where one can meet other players, trade, converse and enjoy the social aspects of the game. Outside of Providence only wilderness awaits, and the further you come from civilization the darker and more dangerous the world around you becomes. Until you reach the deep lumberwoods and no longer have to fear Pilgrims but instead witches and hidebehinds...
So, almost a free-for-all do what you want kind of game with low pc requirement. I've tried the game briefly during its alpha and it's -really- unforgiving.
Try it out, it's not the game for me personally but worth a shot!
http://www.salemthegame.com/