Short answers, pulled from the story.
The final version of Skype 4.0 containing the Silk codec was released on the 3rd of February 2009. This release followed a three-year development cycle that was kept secret until the Consumer Electronics Show in January 2009.
The Silk codec adapts its bit rate from 6 to 40 kilobits per second and maintains an algorithmic delay of 25 milliseconds. It supports sampling frequencies of 8, 12, 16, or 24 kilohertz to provide narrowband or wideband audio options.
Skype Limited announced the public availability of the Silk codec under a royalty-free license on the 3rd of March 2009. The technology was submitted to the Internet Engineering Task Force as a draft on the 6th of July 2009 to become a global standard.
The Opus codec was published as an IETF proposed standard on the 14th of September 2012. This standard was formed by combining the Silk codec with the CELT codec to handle both speech and music.
The Steam game platform began using the Silk codec for integrated voice chat on the 22nd of May 2011. Team Fortress 2 implemented the codec on the 14th of April 2013, and the SteamPipe platform GoldSrc began using it on the 29th of January 2013.