How to install and run
This is an SBT project, so once that is installed simply:
At http://localhost:8080 you will find the Lift part where you can try out the ProtoUser sign up and login features.
At http://localhost:8080/ui you will find the Vaadin user interface which lets you see all the signed up users, edit them and add new ones. As well as try out various features of the Vaadin UI components.
While it is possible to kind-of share the persistence layer between Vaadin and Lift by mapping between Lifts models and Vaadin with a 'data transfer object' or 'view object', this isn't really ideal. A more seamless solution could probably be found if you choose to build your Lift app using the JPA option for persistence. I imagine this would then make it simpler to re-use these objects in Vaadin.