The easiest way to fix this is to ensure liblam4 and openmpi is installed (via the Synaptic Package Manager) and to edit the Makefile.common in the ossim directory ($OSSIM_HOME), changing the MPI_LIB_PATH.
/usr/bin/ld: cannot find -llammpi++
# Open the Makefile.common
# Locate the following line and set its path to
MPI_LIB_PATH = -L/usr/lib/lam/lib