Yes, there are few products at Yahoo! running mojito for production traffic, and there are a bunch on-the-making right now.
There is nothing that prevents you for hosting a mojito app in a regular node.js server. You don't need Yahoo! infrastructure for that. It is a node.js app, just like any app created with express for example.
I second Caridy. On top of that, I have done very extensive stress testing and we ironed out some bugs (as it is expected for such a new platform) in the process and we are now confident that it works smoothly even under high loads.