Morality, like truth, is not something universal, hanging in the air. It is subjective and depends on where you stand. For some, Snowden "exposed NSA's wrongdoings". For others, he "threatened national security".

Regarding the topic of this thread, I know that some people believe that sacrificing anything and everything on the altar of their open-source god is never immoral but the truth is that the sources are Nokia's intellectual property and it is up to Nokia and Nokia alone to decide whatever they damn please with them, however inconvenient it might be for you. Making that decision for Nokia and leaking them would be not only illegal but also immoral.

But, as I say, so are a lot of other things.