I am responsible for the SFLphone project (http://www.sflphone.org/).
FLphone is an open source software phone aimed to provide a professional look & feel and features. It currently runs on Linux but there is a lot of job being done. It supports SIP, and IAX is planned for one of the next two releases. Also Zeroconf is to be supported as soon as we finish migrating our audio layer to the Portaudio library, this shouldnt take more than a few days. Our code has been rewritten a lot since the last 0.3 release, so we can support many protocols/GUIs/audio drivers easier.

We are currently working at a MacOS X version of the phone. Most of the job has done, we just have a few os-specific issues to fix : for example dealing with the mac's 32-bit float audio format and most codec's 16-bit int. I suppose there is an API to convert between these formats in MacOS X, but we have no clue.

Also, it's quite easy to plug a new GUI to our code, that would permit plugging a native Cocoa GUI instead of the current QT one. But once again, our programmer does not have experience with this kind of technologies.

This is a call, I know there may be people here interested in such a project. So if anyone would like to help us by contributing code, graphics, ideas, coffee, remarks or anything, feel welcome !

Our mailing lists are reachable at :
Developers: http://forge.novell.com/mailman/listinfo/sflphone-dev
Users: http://forge.novell.com/mailman/listinfo/sflphone-user
And finally our generic contact address, contact "at" savoirfairelinux dot com

Regards and happy asterisk-ing,
-Jerome