The URL used in the deltarpm spec file leads to a 404 page and needs to be updated http://www.novell.com/products/linuxpackages/professional/deltarpm.html
Fixed in deltarpm-3.5-0.git.20090727 in Rawhide, but because of other changes in deltarpm, fixes won't be backported to Fedora 11 (unless we get xz built for F11).