I noticed the same. Those files should be easy to recognize. Most of them have a name matching "MANIFEST*.MF" and all of them start with the text "Manifest-Version:".
For reference: the format specification is available at as part of the JDK.
These seem to be duplicates too: http://ohloh.net/projects/3374 (which is empty) and http://ohloh.net/projects/3375 (which seems proper).