Today abutcher and I found every way to fail to build VirtualBox OSE from source on OS X. We followed the build instructions on their web site but had some problems. I’ll post a more detailed writeup of what happened and what you need to do to build it later. Until then, here’s a link to download the most recent checkout from svn, built for OS X 10.6 (Snow Leopard). And here’s the SHA256: