He may yet be prosecuted for perjury. However it is very rare because it is hard to prove. There is some "wiggle room" in how he interpreted the question and his answer. Perjury is difficult because you have to prove that he lied willingly with the intent to deceive. Wyden put him in a tough spot, if he answers with 100% honesty he is breaking the law by releasing classified information. If he lies he is committing perjury. If he refuses to answer it could be seen by the public that he is acknowledging the program. So it seems like he chose the route of lying as little as possible and hoping for the best. Part of the reason Congress doesn't like to prosecute perjury is that a lot more people would refuse to answer questions at all for fear that an honest answer would be seen as perjury and they would be punished. More on reddit.com

yes, if Manning/Snowden are traitors for breaking the law then he should be measured with the same yardstick.

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I think he explains it right here.

https://icontherecord.tumblr.com/post/139489829858/why-did-you-lie-about-nsa-surveillance-in-front-of

"When Senator Wyden asked me the question I simply didn’t think of the business records telephony metadata, at the time stored by NSA and governed by Section 215 of the Patriot Act. Instead, I thought of content - given his reference to “dossiers” - which, in my mind, meant Section 702 of the Foreign Intelligence Surveillance Act which governs collection on non-U.S. persons overseas.
My statement about inadvertent collection could only apply when we incidentally collect on U.S. persons who are communicating with non-U.S. persons overseas. The statement makes no sense in the context of Section 215, which he was asking about, and only makes sense in the context of Section 702, which is what I was thinking about.
Even if I had been on the same page with Senator Wyden, I would have still been in an awkward position because the existence of the program that he was asking about was classified. We were in an unclassified hearing, and I thought we were talking about an unclassified program.
So, yes, I made a mistake. But I did not lie. There’s a big difference.
J."

It seems ridiculous to prosecute him over this but you can be the judge.

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If James Clapper had admitted it he would have been committing a crime to answer since it would have disclosed classified information. As a member of the Senate Select Committee on Intelligence Senator Ron Wyden would have been given briefings on the program and would have known the answer to this question before asking it. More on reddit.com