Hello,
I tried to load the gsll in my mac, but gsl is installed by macport in /opt/local. I made a little path to search in the other paths on darwin.
I also created a git repository for gsll in my personal site:
http://www.lambdatau.com/git/gsll.git
With two branchs: master with the svn version and mac with my changes.
Cheer's