I just downloaded an old mod for Kotor 1 that is about 75 MB. It has multiple modules that have the "Sle_" in their names, several Sleheyron textures and voice files that reference Sleheyron. Huh... what did I find. :/
Judging by the screenshot of "Sleheyron" I saw on their website, I'm guessing it's just a bunch of Tatooine modules with Sleheyron skyboxes. That feels out of place.