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).