The main reason these companies don't want anyone not bound to their contracts getting ahold of the source is that changes require re certification, and amateurs changing the code without knowing what they are doing can have some rather bad side effects.
I can see how obfuscating the source would help with that, but what says that they have to change anything in the first place? If they find a version of your code that they like, there's no reason that they have to accept the next version in order to stay with the version that has been certified.. There's a reason that mainframes still exists; it's called legacy software.
Feel the white light, the light within
Be your own disciple, fan the sparks of will
For all of us waiting, your kingdom will come