Two major issues: http://skype-open-source.blogspot.com/2011/06/skype-under-rc... || Copyright (c) 2004-2009 by VEST Corporation. || All rights reserved. Strictly Confidential! The project is using existing code, and "All rights reserved" is not an approved OSI license I believe ;)

And things like compression algorithm are patented, and that's very likely skype is using some of it. Reminds me of a project by Intel of providing an implementation of g729 (a voice codec). The source was available, but it was "non commercial usage only" because of the patents mostly.

An interesting project, but doubt we'll see any usable implementation anytime soon IMO. And even if it does, skype will probably alter a bit the protocol to make it fail if it reaches a critical mass.