Bukkit made it really far with community extensibility via non-official APIs. Now they get to help define the official API based on real-word experience about what developers want to do with customizing Minecraft. They also recently announced that they are merging single player and multi-player, creating a single mod-able codebase.
http://www.mojang.com/2012/07/minecraft-1-3-info-snapshot-w2...
Bukkit made it really far with community extensibility via non-official APIs. Now they get to help define the official API based on real-word experience about what developers want to do with customizing Minecraft. They also recently announced that they are merging single player and multi-player, creating a single mod-able codebase. http://www.mojang.com/2012/07/minecraft-1-3-info-snapshot-w2...