Basically it's just like AIR. You install a framework to launch applications. The Lark framework is composed of XULRunner, Ruby and some other stuff.
Then you download the Lark SDK to deploy your applications. If you already have a Rails application, you just need to package it and it's finish ! You can customize it with an application icon, a menu bar and more !
Creating an application is just creating a Rails web application. You can develop it with your browser and when it's finish, your application is ready to go.
Check out Lark
These details are provided for information only. No information here is legal advice and should not be used as such.