I just finished testing SEAM app with GWT Hosted Mode, and it is possible.
I'm not a GWT expert, but you are required to run the WAR that you plan to develop with on the application server, then when developing in hosted mode it will go to root HTML page, but from there use the Hosted GWT environment.
As for 'seam components', the Seam/GWT RPC calls are working fine if that is your intent.
Can you provide some details on how you did this? I am trying to set up seam with gwt hosted mode as well.