ILU is a distributed process system developed by Xerox. It pre-dates CORBA and later versions supported the CORBA wire protocol and supported C and C++ stub generation from a subset of CORBA compliant IDL files.
Originally (pre version 00-21-00) the OnlineSoftware used ILU as its CORBA implementation. From 00-21-00 onwards, ILU is repaced by OmniORB.
See also AcronymSoup.