It looks to me like you can simply delete the directory then drop any related database schemas/objects. There should be a "mvdemo" schema, if you did the "Tutorial: Learning Oracle Maps by Example". I did the tutorial and do have this user/schema.
I believe this should work since the kit software was simply a set of "unzipped" oc4j jar files in the first place. No registration with the OS other than the Java CLASSPATH.