You can run eDir 8.7 on win2k, or linux, or Solaris or whatever you want (pretty much!) Groupwise 6.5 will run on Win2k as well.
That said, I'd upgrade to NW 6 and run GW in the NLM version and get the file system security and stability. Novell is basically giving away eDir to the cost to upgrade is just time and effort. You can sync eDir with AD via DirXML also.