OpenSky was a service provided by Gizmo5, which is now out of business, to enable communication between users of SIP (Internet standard RFC 3261[1]) and users of Skype (which uses a proprietary protocol).[2]
Early solutions to communication between the two classes of user typically required installation of a gateway.[3]
OpenSky – the first freely available hosted SIP to Skype gateway service[4] – commenced on 9 February 2009.[5]
In March 2009 Skype announced a beta of Skype For SIP, a comparable service for business users.[6][7]
On 30 July 2009 Digium, Inc. announced the opening of Skype for Asterisk Public Beta[8] (prior to the open phase, from 25 September 2008, Skype for Asterisk Beta was apparently non-open[9]). The download was available until 7 August 2009 and scheduled to expire on 30 August 2009.[10][11]