I can define the target runtime here: Select the project->File->Properties->Target Runtimes.
Thanks for the reply,
I already defined the JBoss AS runtime at the Targeted Runtimes but it doesn't do anything.. I still get that error on the project.
I somehow need to associate the seam project with the jboss runtime that exists there but when i click on the Server (in the File > Properties) I don't have any "add" option, it just states that "The project is not associated with any servers".