I have been told that Paraview is one package that
exhibits this problem with undefined environ symbols.
This will occur in any package which creates its own
shared libraries that link in any openmpi shared library
that contains the undefined environ symbol. I think it
is unreasonably restrictive to force all the application
developers who use openmpi to avoid creating shared libs
that use openmpi shared libraries. Again from the
response on the Darwin mailing list this is expected
behavior on Darwin. I will send two patches shortly
that address this without needing to touch configure.