Version 5 comes with a free trial of group video calling, allowing to call up to four friends. After the beta test, this feature became paying. At least one person on the call needs now Skype Premium or a group video subscription from Skype Manager to use group video call (monthly subscription).
Skype offers free Skype-to-Skype voice and video calls and free instant messaging. Calls to public fixed and mobile phones, Short Messages (SMS), voicemails and other value-added services are billed by Skype. Several payment options are available. Skype is available for Windows, Mac OS X, Linux, mobile phones and some Television sets.
Skype offers an excellent support with user guides, troubleshooting guides, FAQ‘s, forums, knowledgebase, different blogs (Big Blog, Community blogs, Technology blog, Business Blog, International Blogs, Heartbeat) and a development site (Skype Garage).
A new software development kit (SkypeKit) that enables hardware and software makers to add Skype functionality to their devices and applications is available to a limited number of beta program developers. A public Skype API enables third-party applications to communicate with Skype. A hardware and software certification (skype certified) is provided by Skype.
The audio codec preferred for Skype-to-Skype calls is SILK (Super Wideband Audio Codec). Skype has contributed the SILK source code to the Internet Engineering Task Force working group.
For Business Skype offers Skype Connect and Skype Manager. Skype pays a special attention to sound and video quality.
A funny third-party application for Skype is Crazytalk.
Skype was founded in 2003. It’s based in Luxembourg, with offices in Europe, the US and Asia. It’s owned by an investor group led by Silver Lake and which includes eBay Inc, Joltid Limited and Skype founders Niklas Zennström and Janus Friis, the Canada Pension Plan Investment Board and Andreessen Horowitz.
I updated my Skype version to 18.104.22.168 in october 2011.