Kevin van Vechten's talk was billed as "Customizing Mac OS X Using Open Source." Instead it was more about making your software buildable on OS X. That's OK. One tool he talked about was darwinbuild, a tool for managing software builds on OS X. Typing "darwinbuild" bash, for example, downloads the bash sources from the OpenDarwin Web site and builds it. Darwinbuild grabs just what you need and sets it up for the OS X build you have on your machine--or any release you choose.