Is the ToolTalk Service the Sun implementation of the Common Object Request Broker Architecture (CORBA)?

No. The ToolTalk service is not the Sun CORBA-compliant Object Request Broker (ROB). The ToolTalk service was designed and shipped in 1991 -- before the Object Management Group (OMG) CORBA specification was defined.

The Sun CORBA-compliant ORB is the Distributed Object Management Facility (DOMF), which is part of the Sun Project DOE product. Sun is publicly committed to support the ToolTalk API running on the DOMF when the DOMF becomes generally available as part of Solaris. Applications that use the ToolTalk messaging service today will transition to the distributed object environment of the future.