Be aware that the 1.0.2 release of fedora-ds is a “transitional” release; it’s moving toward Fedora Core 5 support, including easier Java configuration. However, it does not yet support FC5, nor does it install easily on Fedora Core 4.
Save yourself massive trouble and wait for FC5 for further releases of fedora-ds. To evaluate the directory service, however, consider installing fedora-ds 1.0.1, which sets up easily.
See http://directory.fedora.redhat.com/wiki/Install_Guide#Installation_via_RPM for this option.
Download from http://directory.fedora.redhat.com/wiki/Download; scroll down the page to find the 1.0.1 release rpm.
Visit http://directory.fedora.redhat.com/wiki/Building. Especially look at the dsbuild tool, which manages the whole process automatically, if not painlessly.