Milo widzec rodaka na zagranicznym forum :). Najpier wiec odpowiadam po polskiemu :). Tak, mozna ale osobiscie znam tylko metode za posrednictwem 3d studio max. Pod adresem
http://jedidreams.codealliance.ca/cgi/news.pl) znajduje sie plugin z importerem plikow glm. Potem spokojnie mozna to wyekspediowac do xsi (przy uzyciu pluginu dostepnego z toolsami).
Now in language, which most users of this forum should find more suitable :D.
Yes, it's posiible. Although AFAIK you need 3d studio max to do it. Link above points to glm importer plugin for max that should do most of the job. Then, using xsi export plugin which comes with JO tools you can save it as xsi.