#install kernel headers
sudo update
sudo opkg install kernel-headers
# should have /usr/src/linux-3.2.42 (or similar) 
# should match uname -r? (mine is 3.2.18)

# on ubuntu, rebuild the rpm for arm (?)
rpmbuild --rebuild --target armv7l-unknown-linux-gnueabi ~/Downloads/40002086_S.src.rpm

# but then alien can't make it...

sudo alien -d --scripts rpmbuild/RPMS/armv7l/dgrp-1.9-31.armv7l.rpm 

rpmbuild/RPMS/armv7l/dgrp-1.9-31.armv7l.rpm is for architecture armv7l ; the package cannot be built on this system