This is a port of the Asterisk PBX to the Apple iPhone. It is still in early testing, but it complies, runs, and handles calls without issue. All the code is released under the GPL v2. Tested with iPhone firmware 1.0.2, not tested with 1.1.1.
Feedback is much appreciated. If you are using Asterisk on your iPhone successfully, or are having issues, or have some patches, please let the author know. http://www.mgamble.ca/oss/iphone_asterisk/