The Speaker of House says he is, saying the revelation of " important national security programs to help keep Americans safe and give us tools to help fight the terrorist threat we face . . . puts Americans at risk." I'm no expert, but I'm not quite sure that the revelation of a program that has already been referred to constitutes a risk. I'd be interested in a discussion of whether this revelation jeoparizes national security.
Two U.S. Senators tweeted that he is, but without giving a reason.
A University of Chicago law professor says he is not a traitor, but is "a criminal who deserves serious punishment. . . . Snowden knowingly accepted a position of trust in his relation to the government. He did not have to accept his job, but he did. A clear condition of that job was his voluntary agreement not to disclose any classified information - that is, information the disclosure of which could reasonably endanger the security of the nation."
He argues that is Snowden had concerns about the program, there are legal processes in place that involve constitutional officers where that decision can be made.
Jeffrey Toobin agrees that Snowden is a criminal, but does not seem to comment on the question of whether he is a traitor according to the Constitution.
A writer in Bloomberg criticizes the Speaker and other for not knowing what "treason" is. It does not fit within the narrow reading of the Constitution, in fact few cases do:
Treason cases, in fact, are rare: Fewer than 30 Americans have ever been charged with the crime, and none since the aftermath of World War II.
Not even John Walker Lindh, who fought alongside the Taliban when the U.S. invaded Afghanistan, was accused of treason. Lindh was originally charged with conspiracy to commit murder and terrorism, but he took a plea bargain on two yet lesser offenses.
. . . Why do U.S. prosecutors avoid treason charges? One reason is that the standards of evidence are high: The Constitution requires "two witnesses to the same overt act." Another likely explanation, however, is that treason convictions simply aren't worth the trouble. Most traitors can be put away for life on several counts of espionage and conspiracy. That's less work for the prosecution.
So the answer seems to be no.