Full source code is available. As of June 1999, the current version is 2.7.1. JacORB JacORB is a free ORB written in Java. If you like, you could also add that it comes with a name and an event service implementation. ORBacus is free for non-commercial use.
Source code is also available.
It is available in source code form. ILU The Inter-Language Unification project from Xerox. DOME DOME is available free for personal use on the PC-Linux platform. This is a work in progress. 2.0-compliant ORB written entirely in Java and published under the GNU public license.