Part of the EULA in every commercial program(unless it was not thought through properly) bans the user from, in anyway, decompiling/disassembling an application/library to view its contents.
The reason this is prohibited is because you could come up with some wonderful compression algorythm and someone could decompile it and steal it unless you patent it which still doesn't apply in some countries. But like I said, an obfuscator makes code almost impossible to understand and the really good ones can format the code so it can't be reassembled, at least easily.