GNU Emacs 19.x and above do not compile out of the box on OpenVMS.
Richard Levitte <levitte@lp.se> is distributing and maintaining a
version of Emacs (currently based on version 19.28, but soon moving to
19.34 and then 20.1) that compiles and works on OpenVMS 5.5 and above
on both VAX and Alpha architectures.  For more information see

  http://vms.gnu.org/software/released1/emacs.html#get_emacs_1928_kit