It seems like they use some of the same syntax of hx-get and hx-post, but then some of the templating like you see in apline.js. But no mention of either project. This primatejs appears to be more of a node backend and provides some variation of the htmx library.

They do reference upstream in this one issue: https://github.com/primatejs/primate-htmx/issues/1

Definitely needs some explanation - at first glance this looked like someone trying to repackage htmx under their own name.