I've not looked into exploit code in quite a while, so I spent a little while reorganizing it to see what it does. As you mention, it performs the file manager features you mention, but also has some database exploration functionality, too. Not particularly malicious in itself, that I can see, but it's not something you'd put on someone's system unless one had larcenous intent.
It's kind of painful to look at, though, as the code is a mishmash of styles (functions called with & vs not), repetitive (bits of code pointlessly repeated), buggy (poorly formed HTML, and mostly crap.
When your only tool is a hammer, all problems look like your thumb.