I can't say for sure, but I believe they mean your epub must pass the epubcheck version 1.0.5. I seem to recall having read somewhere also, that Apple has other requirements (maybe e.g. no embedded fonts, certain maximum cover art size?) that if not met will be reported as epubcheck failures, even though they actually are not.
ETA: I think they mean the epubcheck-1.0.5 you can get at
http://code.google.com/p/epubcheck/downloads/list