BSD uses files xx.dylib where most other platforms use xx.so .
I have not found a discussion of the ramifications of the difference.
I changed file "configure" to look for libpthread.dylib instead of libpthread.so .

I specified --thread while invoking configure.
"configure" then found POSIX threads.

The following errors then emerge:
gcc -c  -w -I/usr/include  -DHAVE_POSIX_THREADS    -DHAVE_UNIX   parallel.c
parallel.c:67: error: `_POSIX_THREAD_THREADS_MAX' undeclared here (not in a function)
parallel.c: In function `genie_parallel_units':
parallel.c:315: error: `_POSIX_THREAD_THREADS_MAX' undeclared (first use in this function)
parallel.c:315: error: (Each undeclared identifier is reported only once
parallel.c:315: error: for each function it appears in.)
parallel.c: At top level:
parallel.c:67: error: storage size of `context' isn't known
make[1]: *** [parallel.o] Error 1
mv: rename a68g to ../a68g: No such file or directory

To parallel.c I added:
#define _POSIX_THREAD_THREADS_MAX 4
I have no reason to think that this is safe.

I modified the file "configure" to append IEEE_754_FLAG=-DHAVE_IEEE_754 to BUILD_FILE
even though neither header files ieee754.h nor ieeefp.h could be found.
The compilation finished and a few test cases ran.

It runs some slightly non-trivial test cases correctly.