From what I can tell this was originally motivated by bugs in the German version of the game. Back then 1.1.2 was to be the last version of Terraria (a running joke at this point, they announced 1.4.4 a little while ago) and so decompiling seemed like the best option to get those bugs fixed. This might be a more interesting blog post on that topic: https://thevamp.cc/2012/07/16/terraria-1-1-2-zu-terraria-1-1...