[GRASS-dev] r.roughset - license information

[g_massa at libero.it]

My new grass module, /r.roughset/ (http://grass.osgeo.org/wiki/GRASS_AddOns#r.roughset), make a geographic  rough set analysis for discovery knowledge. It is based on rough set library (RSL ver. 2.0 - M.Gawrys, J.Sienkiewicz) that I've downloaded as C code several years ago from ftp address (ftp://ftp.ii.pw.edu.pl/pub/Rough ) without license indication (public domain, I think). Now, both ftp  and e-mail address are inactive and the RSL project look died.
Rough set geographic analysis is really interesting, I think, and I'd like maintain RSL basically for r.roughset GRASS module develop. So, the questions is: can I add a GPL license at all RSL code ? Otherwise I have to add GPL license only on GRASS module and leave the RSL kernel out of module.
Could anybody help me?

gianluca