Actually Skype's motivation is different. Their system operates under an assumption that all its parts are genuine, and so it places implicit trust into every

Actually Skype's motivation is different. Their system operates under an assumption that all its parts are genuine, and so it places implicit trust into every client and expects it to operate fairly for the system's overall benefit. You open this thing up and there will be 3rd party nodes that do not comply with system's semantics -- supernodes become few and far between (why the hell would anyone be willingly relaying the traffic while on any sort of metered connection?), someone would add an encryption overlay disabling any "lawful interception" provisions they have in place (which they most certainly have or they would've been simply blocked all over the world), someone else would find a weakness in their p2p encryption and start eavesdropping on relayed calls, etc. Does Skype needs this sort of headache? No. Hence the highly obfuscated and encrypted binary with numerous anti-debugging and anti-reversing traps, and their very active suppression of reverse engineering attempts. Skype would basically stop working if it is ever open.