Minecraft Middle Earth is a Minecraft community that recreates the world described by JRR Tolkien and his writings. Everyone can participate in organized events in which we collaborate to create major landmarks, terrain, caves, castles, towns, farms and more.
Effectively as of this time it is on 1.10.2. But older clients are supported, so are new ones.
Clients on 1.4.7, any 1.5 or 1.6 or 1.7 or 1.8 or 1.9 version can join, but there may be issues (no automatic resource packs for example or getting disconnected every once and a while). The older support may be dropped though when the issues become too problematic for the clients, and they will be encouraged to update.
The newer clients such as 1.11 can also join, but with reduced functionality (no new blocks or functions).