Ted Shelton makes a very good case in in VoIP Magazine as to why Skype should open up their protocol to other partners.  From what I see, Skype have had great success attracting development partners to using their API, and surely opening up the protocol is just a logical extension of that?  It’s just that while the API allows applications to do a lot of things, there are some areas that it cannot address. 

I meet people that want to do just what Ted Shelton is talking about, and actually implement alternative Skype client software.  Some want to create Skype gateways, for example tromboning Skype calls to other VoIP or TDM calls under their control.  Some want to use Skype’s IM and presence information as part of a larger VoIP platform.  I use and like the Skype client software, but I can see that Skype’s power is not in the software; it is in the number of desktops they own.  Skype’s would-be partners want to touch that user base too.