A distributed group activity network system and corresponding method over a computer network. It synchronizes and provides access by system users to shared data files of a group activity. The distributed group activity network system comprises one or more server computers and client computers that are connected to the server computer(s) by network connections. Each of the server computers comprises a network server and a memory system. The network server runs on the server computer and provides basic network services that are available at the server computer. The memory systems of the server computers store synchronization files and shared data files of the group activity. Each of the client computers comprises a memory system and a system module running on the client computer. The system modules of the client computers use the memory systems of the client computers and the available basic network services at the server computer(s) to synchronize and provide access to the shared data files by the system users by also using the memory systems of the client computers and the available basic network services at the server computer(s) to synchronize access to and access the synchronization files.