Probably just a stripped down Tcl. Most of the code was written years ago in a week or two, i've only added minor stuff (like a few new functions), improved performance a bit and fixed bugs since then. And the Free Pascal implementation, of course, but that was also done years ago. I've used it in a bunch of my own projects and i've heard a couple of others using it too.
TBH i do not have much experience with Tcl itself outside of writing a few Tk utilities to automate a few bits on my job some years ago. I followed its approach mainly because it sounded like a good combination for being very simple to implement and very flexible to work with, making it ideal for a hosted scripting language (though it doesn't fit all tasks - far from it, especially in places you want even a hint of performance).
So i can't really judge how exactly it differs from Tcl language-wise. It is not compatible as it provides much fewer functions and those work in a different manner. For example there isn't uplevel, but there is upeval which works in a similar manner (though the depth is always one but they can be nested) and there is also downeval (used through upeval to evaluate code back at the environment from where upeval was called), topeval (like upeval but at the toplevel environment), enveval (eval in a function-like environment with optional variable passing in and out) and jaileval (eval in a new, optionally clean, LIL context). Also there isn't much in terms of state notification outside of watch (which i think it works like Tcl's trace but only for variable writes).
I think the syntax is compatible with Tcl (i haven't done any excessive testing to be sure though, LIL was done mainly by "eyeballing" Tcl) so it could be possible to write shims in LIL to be able to write code that works in both, but TBH i wouldn't rely on that.
So i call it just "Tcl-like" in the same sense that JavaScript is a C-like language.