[deathcap]

> Should have been implemented in Java :/

If you are looking for an open source Minecraft-compatible implementation in Java, I humbly suggest (shameless plug) checking out https://github.com/GlowstonePlusPlus/GlowstonePlusPlus. Glowstone++ like TrueCraft currently only implements the server portion, and it has some differences such as targeting 1.8.4 compatibility not 1.7.3 beta, but being implemented in Java has some significant benefits.

For those not aware there is a huge ecosystem of additions available for Minecraft written in Java. This includes thousands of "Bukkit plugins" available from http://dev.bukkit.org/categories/, Spigot plugins from http://www.spigotmc.org/resources/, and now an emerging community of Sponge plugins from https://forums.spongepowered.org/c/plugins/plugin-releases. Writing Minecraft-compatible software in Java has the advantage of being able to potentially support these plugins. Glowstone++ in fact implements much of the Bukkit API and Spigot API, as well as (currently a small subset of) the Sponge API through a bridge. Based on the original Glowstone server, Glowstone++ is completely open source, yet it ties into the existing "Minecraft" plugin development ecosystem.

Java has some disadvantages of course as well, so it's good to see alternative implementations in other languages (not only C# TrueCraft, but C++ MC-Server, Rust Hematite, JavaScript PrismarineJS, etc). The more choice the better =)