Are there some technical details?

The news article states that "Students can even create custom blocks and items within Minecraft by importing new textures" which would require a client side modification and can't be done by importing textures. The actual website says that you modify the server which doesn't allow as many modifications.

There are some bigger cuatomizable server mods around already (hMod, bukkit, spigot, glowstone, sponge, ...). Does this use any of these servers and their API?

If so, does this use one of the existing JavaScript plugins or are they using their own wrapper for the server's API?