An employee of Skype announced on Nov 02. 2009, Skype will publish the source code of their user interface. The planned release date is unknown, details are also unknown.
The proprietary Skype protocol remains closed, in future you will install a closed source library on your system and there are chances that you can choose between more then one user interface.
Not only different GUIs are possible, the Skype protocol can also be used as a back end for any other voice or chat application e.g Asterisk users can profit, as the now available Skype-extension is only for paying customers.
The future will be quite interesting, lets see what actually comes from Skype..
http://share.skype.com/sites/linux/2009/11/skype_open_source.html
Have fun!
