From http://www.macruby.org :

> "MacRuby is a free software project by Apple Inc. Sources are available under the Ruby license."

But it's really more a sponsored project, not a project in the same sense as WebKit. It's more of a "sure, work on it and see where it goes" thing.

I'm not sure I agree. It was started by an Apple employee, endorsed by Apple, 90% of all commits is done by Apple employees, and is hosted on Mac OS Forge (http://www.macosforge.org/), where Apple releases its open-source projects (Webkit, launchd, libdispatch, etc.)