Wired says that the documents were released as a result of Levison's continued efforts for transparency with the case. After shuttering the service, Levinson kept after the government to unseal the court case and release the documents. The motion he filed to vacate the the non-disclosure order was denied, but the court did tell the attorneys involved to release all the documents but to keep the "identity of the subscriber [Snowden] and the subscriber's email address" redacted, but everything else unredacted.

That didn't work out entirely as planned and an August 2013 document recently revealed what we'd assumed all along. Whoops. Hit the source link for a peek at the appeal transmittal sheet for yourself.