I'm no Java programmer, but obviously you'd have to decompile and deobfuscate the code. Then you'd have to find the part of code where it needs the authentication, that's why the link you gave me - it's a CRACKED Technic / Tekkit launcher. Kind of like how some PAID clients (hacked clients) are cracked. When they are, they basically remove the HWID/Mac Address authentication code, and then anyone can use it.