A quick search leads to an enthusiastic article ("whoa! rhinola rocks!") on the haboglabobloggin' blog (which just went offline while I was writing this...), but the author mentions that the current incarnation of the software requires quite some Linux admin-fu to get it working; I assume this will change over the next year as the product matures.
Rhinola is currently based on the Servlet-container mod_gcj, but apparently could easily be ported to other environments (someone called hns comments on haboglabobloggin': "possibly, rhinola might become bigger than mod_gcj, so it will eventually start a life of its own". And he adds: "basic performance is very fast.") Rhinola is as close to mod_js as it can get.
Just in case you wonder about why this is such exciting news to me, I'll repeat an excerpt from the first article I wrote on this topic:
I'm not actually in a position to compare the technical merits of each of the popular scripting languages available, but I couldn't care less which of them has briefer syntaxes for string operations, better database support, better libraries etc. What I do care about is the amount of time it takes me to get into the zone with the tools I'm using. I'm changing contexts on a regular basis, which means I have to be fluent in a lot of tools, not necessarily in-depth, and the amount of time it takes me to get re-acquainted with a software is directly related to my productivity.