Use openmpi-1.4, which was released 2009-12-08 (minor security fix).

According to the openmpi release information:
- Use GNU Libtool 2.2.6b to build Open MPI, which updates the
  embedded "libltdl" library to fix a potential security
  vulnerability. There are no other changes compared to Open MPI
  v1.3.4.

For development purposes it should thus be adequate to simply

    ( cd $WM_THIRD_PARTY_DIR && mv openmpi-1.3.4 openmpi-1.4 )

if you don't wish to recompile things.