v.in.redwg requires GNU LibreDWG. To get this library go to
http://gnu.org/s/libredwg (no official release yet, you need to check out the
source code and compile).

Warning: some trick might be needed to build it since I created the Makefile
while attached to the main grass tree (svn trunk). I did not try to build it
after committing to the GRASS-Addons-svn, but I will try to fix it and clean up
the code soon.

Not to mention that this is still in alpha stage, as LibreDWG, although I
managed to get some concrete results. Not all entity types are supported
(warning printed).