Since there are both Python and Ruby apps on the Mac App Store I would imagine an embedded V8 engine would be allowed. I can't find anything in the guidelines that suggests otherwise.
The guidelines do however explicitly state that "Apps that download or install additional code or resources to add functionality or change their primary purpose will be rejected".
So, as long as your app doesn't download any code, you should be ok.
You can read the Mac App Store Approval Guidelines here.