I am Boris Gjenero <bgjenero@sympatico.ca>.  I am not the author of
G-Force; I only ported it to Unix.  The source that I started with did
not come with a COPYING file, and although I have contacted the author
I haven't gotten a response yet.

I only wrote the source in the _Unix-X directory and its
subdirectories.  The _Unix-X/libxpce and _Unix-X/libmfl are being
released under the LGPL.  See _Unix-X/libxpce/COPYING for more
information.  Note that I consider libmfl and libxpce to be separate
libraries.  They're only being distributed along with this package for
convenience.

As for the rest of the entire G-Force source, well I can't speak for
the author; here's what he says in G-Force.doc:

  This plugin is open source.  Don't steal the source code (feel free
  to use it, just give credit to where you got it from).

Regarding using the program itself, here's what the author says:

  Use of G-Force is intended only for non-profit and hobbyist use and
  explicit permission to use it otherwise is required Andy O'Meara
  <aco5@cornell.edu>