GRASS source upgrade and distribution rights?

Sat Apr 30 02:05:42 EDT 1994

I read in the grass.intro file that the source is in the public
domain.  Is there is any more info on source upgrade and/or 
distribution rights?

For instance, could GRASS 4+ be freely redistributable via an
actual General Public License?   

T. Turner, tturner at gnu.ai.mit.edu
FSF/Project GNU Volunteer
545 Tech Square, Room 426
Cambridge, MA 02139
(617) 253-8568