Downloading just the latest version of QJS, by following the tutorial,
does not include the index.html file mentioned in the tutorial.
Presented is the "master" zip next to the 0.6 zip. Is there anything else I need, or can I just throw that index file into my 0.6 folder?

It looks like index.html is all that was missing.

...as long as nothing is missing from any of those directories (assets, game, lang, and lib).

That seems to be enough to get it working, and everything else that's mentioned in the tutorial is present.

I have now uploaded version 0.7, which DOES include index.html