This is UniversalCoins, a mod made for Minecraft. It was made open-source by its original creator, TED_996, since he was no longer able maintain it.
Original Minecraft Forum thread: http://www.minecraftforum.net/topic/1833251-162164 Browse here to understand the reasons for specific decisions, also to understand the way the mod works (and is supposed to work). Links to 1.6.2 versions of the mod can be found in this minecraftforum thread.
The concept and rendering code for Vending blocks included in this mod were authored by AUTOMATIC_MAIDEN. This mod was released under the GPL license. More info can be found here: http://www.minecraftforum.net/forums/mapping-and-modding/minecraft-mods/1288386-1-6-4-smp-forge-vending-block