This question comes from the webcast "What’s new in IBM Worklight 5.0.6 " that was held on March 28, 2013:

 Can we run a worklight app (Client only) without WL server component?

Yes - there is a feature setting as part of the Init options for connect on startup.  However - this removes some of the value proposition from the Worklight offering.

let me elaborate on features you wouldn't be able to leverage:
- no governed integration with your back end (lossing point of control and decorelation to ease back-end and front end evolution cycles)
- no app management incl direct updates for hybrid apps
- no off line encrypted & syncable off line data storage
- no authentication framework leverage
- no unified push notifications
- no analytics
- ...