Reading the comments it's clear that majority people do not understand what it is, mostly because the title is misleading.

It's a custom, toy browser with Ruby support, not "Ruby in the Browser" (where the implication is that the browser == chrome or firefox or safari).

I'm just trying to clarify that so that people don't get the wrong impression from the misleading title.

Chill out dude and stop thinking about market adoption. It's about the journey, not the destination, remember ? This is clearly a new creative process that should be treated with respect. This may open the door for seeing other languages in the browser where chrome might like say be bundled with v8, mruby, python vm, etc.

Your children one day will laugh at you saying our parents only had javascript in the browser.

Stop thinking about market adoption.

Since when have we only had javascript in the browser? We've had Java applets. We've had Flash. The issue is security holes. The reason our children will never laugh at us for only using javascript in the browser is because we cared about writing secure web applications.