Any additional information related to these implementations, that came to light after the release of this product, is described below.
The Fortran-aware debugger, dbx90, uses gdb. This is no longer supplied by Apple on Mavericks (on earlier versions it is included in the Xcode command tools). However, gdb can be downloaded from http://www.gnu.org/software/gdb/download/ and built from source (using gcc). It will then need to be signed (self-signed is ok) and installed; following this, dbx90 will work. This has been tested with GDB 7.7.1.
Additional information about this procedure will be available shortly.