What's the exact problem ? Sorry ... I've gone back through this thread but I'm not sure what the
issue is - and rt.cpan.org seems to be down at the moment so I can't even get to the bug reports. I did see an earlier suggestion that compiler bugs may be the problem - but my understanding is that if 'make check' passed all tests (when building the GMP library) then you haven't got any compiler bugs. If GMP has been successfully built and installed then I feel there shouldn't be much of a problem in getting Math::GMP installed ... though, admittedly, I know stuff-all about Macs.
I could speculate about what the problem could be ... but it's probably quicker if someone provides a refresh of the situation.