On BizTalk 2013/R2. I'm following steps here: http://blogical.se/blogs/mikael/archive/2012/05/28/rest-start-kit-for-biztalk-server.aspx.
I have GAC'ed the bLogical.BizTalk.RESTBehavior.dll, and restarted the Host Instances.
I registered the behavior in my WCFCustom Send/Receive When I try to create a new SendPort (solicit/response), I pick the same host instance tied to the WCFCustom adapter I setup, and on the "Behaviors" tab, I do right-click on "EndpointBehavior" and the BizTalkRESTRequetHandler does not appear.
Image below shows setup of WCF_Custom adapter for one host instance.
Image below shows BizTalkRESTRequetHandler not showing in the list.
Found it. I had to close/re-open BizTalk Admin console after doing the GAC.