Hi,
I just got SciLab (a MatLab-like environment for numerics and simulations) running under OSX. It requires XFree86 and some other stuff and includes a nasty hack, but for thrillseekers interested in trying alternatives to MatLab here is a link to my notes from porting it.
http://homepage.mac.com/persquare
NB. they are not exact instructions, so if you havent done any previous porting it I think you'd better wait for a binary...
/Per
PS. I'll get some screenshots up later today...