This code was apparently so pervasive and long-lived that the GNU Fortran compiler added compatibility for DEC extensions less than two years ago, in version 7. There must be enough demand for DEC's additions to have made it worthwhile.
Truth is most of the important ones went into Fortran-90 if I understand it correctly (I'd trust Paul W.s comments if he knows). Again, I'm not a compiler guy, but I've been known to eat lunch with a few of them :-)