Minetest is nearly identical alternative to Minecraft. It's completely free and does not require an account.
Most controls feel the same, so Minecraft players will be comfortable right away. It's lighter weight, and runs on most home computers.
We use our own private server for the club, which means there are no strangers able to access our game space. However, please note that the Minetest software, like Minecraft, does include the option to join public servers. We encourage families to supervise use at home if their child explores other servers on their own.
