I've never heard of a version of Basic called "simple basic".  But there
are several versions of Basic that run on the Mac.  There are at least
five mentioned in the faq for comp.lang.basic.misc:

FutureBasic from Staz,
QuickBasic from Microsoft,
True Basic from True Basic Inc.,
VIP Basic from Mainstay, and
Chipmunk Basic which is a freeware.

The first four include compilers.

But, if you just want to use a simple old-fashioned Basic interpreter,
try <ftp://ftp.rahul.net/pub/rhn/chipmunk-basic-3.2.3.sit.hqx>

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#include <canonical.disclaimer>         // I speak only for myself, etc.

I use PG:Pro and Future Basic. If you start with A pre-written SHELL
program
for, say Text File Reading and processing you can add your own special
text
processing function to the shell quickly and easily without knowing a
lot
about the tool box.

I have written a freeware Shell for Handling Text processing problems
that
I called "TF_Reader". The Archive is an 80k Stuffit Lite "xxx.SIT" file
I
called "TF_Reader_SHELL_v100.SIT". It's in the software library of the
AOL Computing Utilities Forum. I have also passed it up to the
FutureBasic
Web Page http://ids.net/~paumic.futurebasic/