If you are curious about running GRAMPS under Mac OS X 10.4 (aka Tiger), over on the GRAMPS blog, the developers posted an article a few weeks ago about what you need to do.
GRAMPS stands for “Genealogical Research and Analysis Management Programming System”, and is a genealogy program written for Linux and other Unix-like systems (the various *BSDs, etc.), and can be run under Mac OS X with X11 (installed with OS X or off of the OS X CDs/DVDs).