A programming language is under copyright of the creator.
, which can decide to put it in public domain, standardize it, give an open source license to it, whatever.
While NeXT did not exactly created Objective-C, it acquired a license to be able to create their own implementation, which became the official Objective-C compiler.
Plus, lets see what is the outcome of the Oracle vs Google trial regarding copyright.
A programming language is under copyright of the creator. , which can decide to put it in public domain, standardize it, give an open source license to it, whatever.
There's no such thing as language copyright.