The first version supported on all UNIX platforms is 2.3.0. NICI is a shared object (.so) named libccs2.so. Typically, it is a symbolic link to the actual file named per platform and version. NICI does not depend on eDirectory to be installed.
In the DHost environment, NICI has a shared object called libniciext.so, which is loaded by DHost to carry out communications and other eDirectory services on behalf of NICI. The shared object is shipped with eDirectory distributions.