Edit: no, it's definitely a language of some sort:
> The syntax and semantics of Tree Calculus are minimal and self-contained, relying on no platform-specific concepts or abstractions. As a result, it is trivial to write interpreters on any platform or in any programming language (demo). ...
> The ability to bootstrap the full power of Tree Calculus anywhere makes it an excellent configuration as code language in a heterogeneous system. Developers could write Tree Calculus programs that generate, say, JSON, and use an interpreter ...