Okay, I did the research on this.  The Linux Mathematica 3.0 binary is
a statically linked ELF executable, and those don't work on NetBSD 1.2
or, apparently, NetBSD 1.2.1.  NetBSD-current has some heuristics to
make statically linked Linux ELF binaries work.

I tried running Mathematica on a -current machine, and it seemed to
start up fine and do simple arithmetic.  I really don't know enough to
test it out carefully.

The heuristics in -current appear to have gone in shortly after 1.2
came out, so a back-port of the changes should be relatively easy
given the help of someone with CVS access.