In the US only purely creative work can be copyrighted. Basically you can only copyright something if it has no practical application. This means that literature movies and music can be copyrighted but clothing, recipes and industrial design cannot. A fictional language (such as Klingon) could be argued to fall under the realm of copyright because it is not really practical. Google has a fairly strong case that a programming language is not copyrightable. The libraries written using that programming language in both compiled and uncompiled form would fall under copyright though.

AFAIK they won a trademark case, not a copyright case: Microsoft could not fork their own bastardization of Java and still call it Java.

Orc isn't a Tolkien invention any more than the term "elf". Tolkien used these terms in a slightly different way and redefined fantasy using them, but he didn't invent either. Orc, in case you were wondering, is derived from the Latin word "kill" or "killer". Hence the marine mammal "orca" or "killer whale".

No, it's a specific way of licensing your creation.

In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work.

- 17 USC S 102 [cornell.edu]

You can copyright a program expressed in a language, a book describing the language, a compiler or interpreter which implements the language, but not the language itself. Although, if Oracle can get a ruling that a language is copyrightable, then IBM may want to exert a copyright over SQL.

No, copyright is there with or without licensing. Copyright means that nobody can use it (for certain definitions of "use") without your permission. Licensing is giving that permission, usually with certain conditions attached. The two concepts are related in that there would be far less need for licensing without copyright, but nonetheless are very distinct.

The language is defined by (a) rules to decide whether a given source is a valid program, and (b) rules to define the behaviour of any valid program.

For example, I could define a language by stating that a text is a valid program if it doesn't contain any 'e', and the behaviour of the program is to print the number of lines of the text.

That's not a very useful language, but a language. Note however that the sentence above is not the language, but a description of the language. A valid program in the language would be

bhfjdks sdfjk bvcnxbvxc nm,vc.xyn v,yxcb fjkdg ff
gfds gfjdksl mvc,xyäa dvsqwzt z cv ödf hgfdö

Tolkien Estate says it's copyrighted. And, yes, they have been going around and suing people publishing linguistic works on Sindarin and such based on that interpretation. It's pretty well known in the community that deals with those things.

That said, I don't think it ever came to a court injunction. Generally speaking, the enthusiasts don't have the time, the money and the inclination to go to court over such things, so they just back off when threatened with a C&D.