Usage
Join a Minecraft server, open the GUI via the keybind (comma , by default) or through Mod Menu, enter the address of your Sync Server, and click "Connect".
How it works
When you connect, you receive all chunks that your friends have mapped since the last time you played (and were connected to the Sync Server).
Every time any of your friends load a chunk with Map-Sync installed (even if they don't use any map mods!), it gets mapped and the map data gets sent to the Sync Server. It will then send it to everyone else, and if you have a compatible map mod installed (Journeymap, Voxelmap or Xaero's), the mod will display your friends' chunks.
Map-Sync tracks a timestamp per chunk, so old data will never overwrite newer data.