Where can I get this heavily modified Tiddly Wiki on which the documentation runs?
http://wakaba.c3.cx/releases/other/kozakana2.pl is the backend, and for the frontend you just copy docs.html.
I'm not sure I fully understand what advantages the heavily modified tiddly wiki offers over the original variant, in which it seems changes save just fine? Also: how does one go about making uneditable tiddlers?
This was based on an ancient version of TiddlyWiki, that did not save gracefully even locally. And last I checked, the current version still does not support saving back to the server out of the box.
Anyway to copy paste code to make it work with the newest version?
Not likely.