As far as I am concerned, Obj-C and Cocoa are so tightly integrated into each other that using one without the other is a rather pointless exercise.
There are compilers available to use Obj-C (the language) on just about any platform. I guess you could use Obj-C to write GTK or Qt code (I doubt that the Qt preprocessor would like that, though).
If you read that Obj-C is great, that usually means that Obj-C is great for Cocoa. Cocoa and Obj-C make for a great team! Probably comparable to Android and Java or .NET and C#. It ultimately does not matter whether Obj-C would be of much use without Cocoa, since almost all people will be using it as part of Cocoa.
Great tires are of little import if you don't own a car.
There are compilers available to use Obj-C (the language) on just about any platform. I guess you could use Obj-C to write GTK or Qt code (I doubt that the Qt preprocessor would like that, though).
If you read that Obj-C is great, that usually means that Obj-C is great for Cocoa. Cocoa and Obj-C make for a great team! Probably comparable to Android and Java or .NET and C#. It ultimately does not matter whether Obj-C would be of much use without Cocoa, since almost all people will be using it as part of Cocoa.
Great tires are of little import if you don't own a car.