Julia,
RIM, MAPGEN, GCTP, pbmplus and xgen are free ... and, they can be
downloaded from the CERL server (moon.cecer.army.mil) under the
/grass/grass4.1/release/related directory. You'll need to pull down the
archived files 'related.cpio.Z.00**', unpack them and you should be all set.
Later,
Shane
amante@grouse.pnl.gov