The Spacemesh Testnet is a public beta release of the Spacemesh p2p software platform. Anyone with a computer and an Internet connection can join without any permission from anywhere and participate in the Spacemesh p2p network.
The Testnet is designed to test the Spacemesh protocols and software prior to release of the Spacemesh Mainnet and the Spacemesh cryptocurrency. Note that the cryptocurrency enabled by the Testnet is monopoly money without any real-world value.
Spacemesh 0.1 is the name of the first release of the Spacemesh Testnet.
To learn more about the Testnet, Read the Testnet FAQ