Despite leaking state secrets, Snowden's life was never threatened by US officials. Yes, he's a whistleblower, but his actions are far more serious than developing software. Even then, US officials talk of imprisonment at worst.
http://www.foxnews.com/politics/2013/06/11/ron-paul-us-gover...
http://www.businessinsider.com/us-spies-talk-about-killing-s...
http://www.theguardian.com/world/2013/oct/03/edward-snowden-...
Your second link cites Buzzfeed as a source, and the Buzzfeed article[1] claims some unnamed low-level officials would like to kill Snowden. Yet these anonymously-quoted people also admit that they wouldn't do it unless they had approval from higher up. Pretty close, but still not a threat.
Your last link is about a retired government official making a joke in very poor taste.
None of these are actual threats, let alone by US officials. They're either idle musings, or bad jokes, or "I want to, but I'm not going to." I certainly don't agree with the people making these despicable statements, but they're qualitatively different from, "If you don't stop leaking state secrets, you will die."
1. http://www.buzzfeed.com/bennyjohnson/americas-spies-want-edw...
My sister's home town in Michigan says it's illegal to spit on the ground. America threatens jail time for possessing weed!