V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

COSE
       Common Open Software Environment (HP, Sun, IBM, SCO, USL, Univel)


The Free On-line Dictionary of Computing (30 December 2018):

COSE

   Common Open Software Environment.  An initiative by
   Hewlett-Packard, Sun, IBM, Novell, Univel and SCO to move
   toward consistency and interoperability between Unix
   suppliers.