GnuStep is a project that attempts to enable the NextStep vision to live on. It is built upon ordinary unix systems like solaris or linux. It uses the free GNU ObjectiveCee compiler. What they are doing is recreating the object libraries, as well as attempting to clone the look and feel of the GUI. Some key pieces are:
TheoVerelst I tried the example (on Redhat 9.0 Linux) and made a socket based link with Tcl/Tk, it seems practically usable: http://82.168.209.239/Diary/ldiary17.html
See also: http://www.gnustep.org/, GnuStepWeb