I have checked that JBoss 5.1.0 contains Servlet-api.jar and JSP-api.jar which support struts 2. Base on the website http://struts.apache.org/2.1.8.1/ mentioned
I have seen others post questions related to Struts 2 and JBoss AS 5.1.0, so I would say that it probably supports it. But based on the way you are asking the question I assume that you tried it and ran into problems...