OSGi functionality in WildFly 8 is provided through the OSGi subsystem.
The documentation of this functionality can be found at the JBoss OSGi documentation pages.
Integration with WildFly and reference the the OSGi subsystem in the WildFly XML configuration file can be found in the Application Server Integration section.
More information on the OSGi component in WildFly can be found on the JBoss OSGi project pages.