With Forth there are a handful of core words you really need to get things going, some ubiquitous but not mandatory convenience ones, and then it's up to what best fits the platform. There is no such thing as "the" Forth.

Isn't Lisp just the same?

The TI-84+ series is such a specific technological niche that it makes sense to write a Forth customized for it platform, which the author of this OS did earlier[0]. This repo is an OS though, so "Forth-based" means the OS is built on a Forth platform but with enough extra features that it is more than just a Forth language at this point.

Also, arguably, the part where it is compiled through Scheme might make the purists say it's not a true Forth (which tend to be self-hosting).

[0] https://github.com/siraben/ti84-forth

> There is no such thing as "the" Forth.

> Isn't Lisp just the same?

Not really.

Most Common Lisp folks have hijacked the word "Lisp" to mean Common Lisp.

Then you have Lisp-1 and Lisp-2 definitions, so when you say "a Lisp" people will wonder which you fall into, and it'll be one of the first asked questions.

Depending on your audience, they may have a very fixed idea what "Lisp" means, and it may be a very detailed concept.

Forths don't tend to suffer from those problems.

I'm assuming that it's a Forth because there are a lot of dialects, and this is one of them.