Lua is the same. Only false and nil are "falsey".
I remember I fixed a bug in a mod for Minetest that assumed 0 was false and caused an infinite loop.
Yup :) Everything in Ruby inherits Object, too. It's a really neat language, and when you get accustomed to it, you might wonder why some other languages aren't written like it.
For the 0 value being truthy, consider that Ruby is a dynamic language. Imagine if you asked a user how many motorcycles they own. If they answer, you'll have an Integer. If they don't, you'll have nil, from NilClass. 0 is just as valid of an answer as 2, so you can do something like this:
raise NoResponse unless motorcycles
save_motorcycles(motorcycles)
And people bash Javascript as if it was the devil when thinks like this exist on other languages.