Meta keyword tags are not used normally by mainstream search engines in their ranking methodologies (though there are a few exceptions for SEs used in certain countries).
However, it is not a good idea to have identical tags on more than one page of a website and it is against normal conventions to have duplicate meta tags on the same page.
I doubt if you would get a penalty for anything to do with meta keyword tags - but having a mass of duplicate meta tags on the same page may flag a potential attempt at spamming if they are repeated on a page and anything that does that should be avoided.
Having the same content in meta tags on different pages is not useful but won't cause any penalty, but with keyword tags, unless you are using them for a specific purpose of your own (and not for search engines) leave them out. They don't help your rankings at all - so why use something that potentially could damage them through misuse, even if the chance is remote?