Snowden is neither a traitor or a spy, in my opinion.
The word "traitor" implies the crime of treason, and that crime is very narrowly defined in the Constitution. What Snowden did does not meet that definition. He's not really a spy, either. It's highly doubtful that the briefing slides he absconded with really provide any information not already known to countries like China and Russia. It's all pretty general and of not great value to them.
So, what is he guilty of? He is guilty of taking classified information and distributing it to people not authorized to receive it. It's pretty clear that he did those things, and there doesn't seem to be anyone disputing that. Now, that's a serious thing, and could result in a prison sentence for him if he returns to face trial. How long? I don't know, but I'd guess it would be something on the order of 10 years or so.
With a strong defense team, it's likely that they'd be able to show that a large percentage of the information taken and exposed had already been disclosed in public by the government. I know I recognized much of the information from public releases on most of the programs described in the briefing documents. The collection of metadata, for example, has been understood to be happening for years, if a person was paying attention.
That argument could lead to a determination that the TOP SECRET classification, along with the SI and NOFORN additions, was not really needed. There was, in those briefing slides, some information that wasn't already public, of course, but the defense could make a good case that nothing horribly harmful had been released. All of that will go to decrease the seriousness of the crime and lower the length of the term. Witness Daniel Ellsberg, who was tried AND ACQUITTED for something not dissimilar.
If Snowden returns, he can count on spending some time sitting in a prison or jail cell, even before a trial. Clearly, he'd be seen as a flight risk, so it's unlikely that he'd get released on bail. However, with so many eyes on him and the situation, I would think his treatment will be by the book throughout. Anything less would result in continuing publicity, which is definitely not something desirable to TPTB just now.
If Snowden doesn't return, but ends up accepting asylum in some other country, the US isn't going to go kill him. In fact, his death from any cause would be instantly blamed on the current administration, and I'm certain that would not be considered a desirable outcome. Instead, the US would probably try to extradite him, but would also have an interest in making sure he didn't die in some violent situation or at all. As much as the government would like to use him as an object lesson for others thinking about releasing classified information, his untimely death would have bad results and would not be wanted. The government, better than any one else, knows that nothing really important was revealed and that any harm would be minor from the release of these briefing documents.
The bottom line is, it seems to me, that Snowden would best serve himself by letting the Russians know that he'll be OK with getting on one of the daily Aeroflot flights to NYC. Since he has already achieved "hero" status among many, he can be assured of a strong defense team and delicate treatment by the authorities, I believe. Anyhow, that's what I'd advise him to do, if he asked me. He won't ask me, of course, but that's what I'd suggest as the most practical decision for both the short and long term.
My opinion is that this relatively young man is pretty unsophisticated in his thinking about this whole thing and that he probably got some bad advice from people for whom embarrassing the US is far more important than Snowden's welfare. I suspect he has realized that at this point, too, and is very concerned about his future. And that future will depend on the decisions he makes in the next week or month. I hope he gives his choice a lot of careful consideration. I wish him no ill, although I can't approve of what he did and how he did it.
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Edward Snowden is a modern day Paul Revere with a thumb drive full of news that Tyranny is coming!
on that technical term, at least, we can agree.
sounds simular to me 
Let's join together to fight it 
