It wasn't that hard. Mac OS X doesn't include a library that spl needs in order to compile, libfl.a. Get it from ftp.gnu.org, in the directory /gnu/non-gnu/flex. Download the flex-*.*.*.tar.gz file, decompress it, run configure, run make (you may need to edit the Makefile to use cc rather than gcc; I made gcc a symlink to cc, so no issue there), but don't install it. Move or copy libfl.a to /usr/lib, and run ranlib on /usr/lib/libfl.a. Now go into the spl source folder and run make. It should work. The only other issue I ran into was a mispelled filename in the include directory in the spl source folder. Other than that, it works fine.