There is a question that references the old, buggy 3.5 version here. This question is regarding the WF that comes with .NET 4.
My question is, where can I find a code sample and information on hosting the Workflow 4 Designer?
Is Silverlight Supported, or Click Once? What .NET client profiles are supported?
There are several samples out there showing how to rehost the designer. Here is one on my blog and here is another in the MSDN WF4 & WCF samples.
The WorkflowDesigner is a WPF control, there is no Silverlight version available. The client profile should be good enough for almost all your needs. And Click Once will work just fine.