Explain what it is in BIG LETTERS near the top of the page, like http://npmjs.org/
Change the "Download" link (download what? one may ask). Putting "Install" might be better; but "Install LuaRocks" is perhaps ambiguous. npmjs.org has a link with some explanation "beneath the fold". I suspect given their popularity they're a good model to follow if you don't have a better idea.
I mistakenly filed this issue first on the LuaRocks github; add a "Report site bug" link (I know, there's already a "Source" link, that could better be "Site source" as well!).