I don't know about Richfaces 4, but I managed to use Richfaces 3 as a module and actually I needed to patch a few things:
a) In richfaces-api-3.3.3.Final and richfaces-impl-3.3.3.Final, the static Maps
must be Weak
b) In richfaces-impl-3.3.3.Final, the method org.ajax4jsf.resource.ResourceBuilderImpl.createResource(Object, String) must add a failback to load the class from the Current Thread's class loader.
c) In addition, using JSF 1.2, I had to deploy Facelets 1.1.15 as a module and needed to patch MetaRulesetImpl to set the attributes map as a WeakHashMap<Class<?>, WeakReference<MetadataTarget>>.
just for reference, here is the feature request for distributing RichFaces 4 as AS7 module, please vote there or comment if you would like to grab that issue and implement it: