ClasspathHelper.forPackage calls the classLoader.getResource of the ClassLoader. It appears that the IBM's implementation does not work properly or at least doesn't find URLs for the package specified. See this link for a discussion about that: IBM JDK ClassLoader GetResources
It also appears as though Spring has written a class that deals with this type of problem:
PathMatchingResourcePatternResolver
I also tested the snapshot version of the code and confirmed that is does NOT work on WebSphere 7 when I deploy my web-app (WAR).