On EAP 4 isn't possible to set-up mod_jk with httpd from official repository. Version of Apache httpd is 2.0.52, steps followed as described in http://documentation-stage.bne.redhat.com/docs/en-US/JBoss_Enterprise_Application_Platform/5.0/html-single/Administration_And_Configuration_Guide_CP01/#clustering-http-modjk

When starting server, error message shows:
/etc/init.d/httpd start
Starting httpd: Syntax error on line 3 of /etc/httpd/conf/mod-jk.conf:
Cannot load /etc/httpd/modules/mod_jk.so into server: /etc/httpd/modules/mod_jk.so: undefined symbol: ap_get_server_description
[FAILED]

Due to internet search, it's like mod_jk is build against higher httpd version. The same error on i386 and x86_64.