I am not sure anything need to be done to use HTMX in B4X projects. It is not a Java library that need to be wrapped first before it can be used. It is just like using jQuery in B4J server.
You have now a couple of ways already to code web apps. Such as abmaterial, banano. But if you want leverage html (say you have a tailwind or bootstrap or Bulma or any other css framework you like) vanilla jserver + htmx is just amazing.
I was reading about this some time ago. I think also because its on the Github Open Accelerator Program it has potential, a $20K sponsorship makes a lot of sense hey.
I plan to use HTMX in my future web app development but... hey, jQuery is actually working fine... and it works very well with many existing Bootstrap template.