A KnowwledgeBase contains one or more packages, and inside the packages is where the Declared Types live.
So, using this code (I didn't test it but it should work), you can access all your declared types of all the packages in a knowledge base:
Set<String> declaredFactTypes = new HashSet<String>();
Collection<KnowledgePackage> knowledgePackages = kbase.getKnowledgePackages();
for (KnowledgePackage knowledgePackage : knowledgePackages) {
//the key of this map is the simple name of the declared type and not the fqn
Map<String, TypeDeclaration> typeDeclarations = ((KnowledgePackageImp)knowledgePackage).pkg.getTypeDeclarations();
//collect all the keys in the set
for (String type : typeDeclarations.keySet()) {
//store the fqn of the declared types to avoid name collision
declaredFactTypes.add(knowledgePackage.getName()+"."+type);
}
}