I think it's totally possible to port on other firmware. It does not use a special 5.3.2 exploit.
It's basically a big patch of the loader code (the part responsible of loading the rpx and rpl code).
At specific adresses in the code of the loader I put instructions to jump to functions to modify stuff in the loader, and then come back to the loader execution.
In order to port to another firmware, you must find the similar part of the loader code and change a lot of adresses. It's doable but it takes a lot of times and patience, to compare with the 5.3.2 version of the loader. I'm not sure it's interesting to port to a lower firmware.
Exactly, I should have added that in the Readme sorry, you can host it on your computer and access it on the wiiu. By the way, I made a mistake in the loadiine release, in the www folder, the folder "loadiine-532" should be renamed "loadiine" (my server automatically rewrite the url so I forgot to rename it).
It's possible to launch some games only with mii maker (what I did at first), the compatibility can be affected because mii maker is not configured to have a lot of memory.
At first I wanted to add a mode to be able to use mii maker or smash bros to launch a game. But the code is too big for the browser exploit (which is limited). It will handled in a future version.