I jsut checked on the Opensuse Build Service.
There are OpenMPI RPMs available for SLES 11 SP2 - but not SLES 11 SP1
I have got openmpi installed on my SLES 11 SP1 system, version 1.3.2
Zypper says it is rovided by the System repository - so it should be on the SLES DVDs you have.
As an aside, installing Openfoam is not trivial - it even packages up its own version of gcc.