I had my first exposure to Objective-C using GNUstep on a Linux box in about 2002. I am grateful that it existed and it was there for me to be exposed to it; I was pretty young and probably could not have afforded a Mac in those days.

As objc and Apple itself has gained so much steam over the years, it's kind of funny to have learned it long ago via a clone of NeXT stuff. Most folks working in the language have no idea that it could possibly exist outside of Apple and tend to think of all the framework underneath them as a black box. I think maybe some of these folks would learn something by looking at an open source re-implementation of these NS* classes, or attempting such an endeavor themselves, even if on a small scale.

Also: objc is just too interesting for Apple to hog it all for themselves, or for it to be a one-implementation language.