why do we use ~/osmplanet/osmconvert32 ? May be this pattern comes from planet script but I would prefer to change it as well (as dirty/nasty)
My suggestion is 
if [[ -z osmconvert ]]; then
wget -O - http://m.m.i24.cc/osmconvert.c | cc -x c - -lz -O3 -o osmconvert
fi 

or 
wget http://m.m.i24.cc/osmconvert32