Hey there,
I really like gaming cryptos, especially ones which makes sense. I have a few questions.
Is it some kind of mod to Minecraft?
It's not. It's a totally new game, running with its own engine, chain, game rules, etc. The game is in the blockchain itself: every player action is a transaction on the chain, which means that if you have the blockchain, you can recreate the entire history of the game, and verify that every action was within the game rules.
Is it free to play?
Not so simple: anyone can download it and roam around the world. In order to perform actions, however, you need some in game currency - gold - which is either mined or bought off someone else. This system is central to Townforge: most money you spend performing actions (such as buying land, creating a new building, etc) is stored in the town treasuries, and town treasuries regularly trickle back into players' accounts based on how well they are doing in game, so players who play the game well will in fact earn money. But they will have to pay money first, in order to build the structures that will get them this income stream. Moreover, about 9% of the currency issuance is also directed to the town treasuries, which will also trickle back into players' accounts. There are various other ways to get money in the game, so whether you pay to play or get paid to play depends on how you play (and you can choose your specialization: whether it's building structures that get you income, or playing the decentralized in-game markets, or creating stone or wood producing buildings on juicy locations, etc).
You guys hosting the servers, or anyone can create it?
Townforge is a decentralized game. There's no central server. There is a seed node as in many other cryptocurrencies, but it is not necessary for gameplay, just to be able to find other peers on the network. Every node in the Townforge network receives actions from other players (in the form of transactions), and validates them. Mining those actions into the chain makes the game tick. Run the Townforge node and you are part of the decentralized "game server", so to say.
This implies that your in game possession are safe: there's no central server to be taken down, no admins with access to a central database who could alter it, etc. If your in game balance is 1500 gold, it will stay 1500 gold unless either you withdraw it (automated, it's just a blockchain transaction too, you don't ask a central party to send it back to you like you would on an exchange for example). If you created some custom items in game, you have them until you sell/give/destroy them. If you have a nice plot of land near the town square, no other player or admin or the like can take it from you. Because these things would be against the game rules, and every node, including yours, validates actions.
So if I were to get hit by a bus, then the seed node crashes, Townforge would still continue ticking happily as long as there are miners on the network.