This is a very early alpha of ZFS on OSX, to be the next generation of MacZFS.
This is spl.kext, the Solaris Portability Layer (SPL), a dependency of zfs.kext.
It is tested primarily on Mac OS 10.8.2 and secondarily on 10.6.8, with the latest Macports.
See https://github.com/zfs-osx/ and http://MacZFS.org/ for more information. Note MacZFS's wiki on kernel development and panic decoding.
OSX claims that gcc has to be version 4.2 Hopefully the path to /System/Library/Frameworks/Kernel.framework is universal.
git clone https://github.com/zfs-osx/spl.git
# ./autogen.sh
# ./configure --prefix=/usr/local
# make
# rsync -ar --delete module/spl/spl.kext/ /tmp/spl.kext/
# chown -R root:wheel /tmp/spl.kext
# kextload -r /tmp/ -v /tmp/spl.kext