This is SAGE -- open source mathematical software.

         http://www.sagemath.org

1) Download the dmg somewhere and double click on it.
2) Drag the sage folder somewhere, e.g., /Applications 
3) Use finder to visit the sage folder you just copied it and double click on the "sage" icon.
4) Select to run it with "Terminal":
     Choose Applications, then select "All Applications" in the
     "Enable:" drop down.  Change the "Applications" drop down
     to "Utilities".  On the left, scroll and select "Terminal".
     Click "Open", then in the next dialog select "Update". 
5) SAGE should pop up in a window.
6) For the graphical notebook, type
     notebook()
   and follow the directions, which are to open firefox or safari (your choice)
   to the URL
       http://localhost:8000
   If you are on a single user machine, using inotebook() is a little easier.
7) Email
      http://groups.google.com/group/sage-support
   with any questions.  


If you're an OSX guru and want to make steps 4--6 much nicer, 
join sage-devel and tell us.  You'll be greatly appreciated 
by a lot of people!
           http://groups.google.com/group/sage-devel