Arquillian only needs to know where JBoss AS is installed when using the managed container (e.g., jbossas-managed-6). In this case, Arquillian manages the lifecycle of the container and therefore must have access to the startup script. The installation path is read from the environment variable JBOSS_HOME.
When using the remote container (e.g., jbossas-remote-6), Arquillian simply needs to know that the container is running and communicates with it using a JNDI lookup. The JNDI settings are set in a jndi.properties file on the classpath (typically in src/test/resources-jbossas). You also have to set the remote address and HTTP port in the container configuration if they different from the default values (localhost and 8080, respectively).