This link may help clear up the confusion between KeePass 1 and 2. (<a href="http:&#x2F;&#x2F;keepass.info&#x2F;compare.html" rel="nofollow">http:&#x2F;&#x2F;keepass.info&#x2F;compare.html</a>). As for the KeePassX, this was a port from the Windows KeePass 2 to mac OS X. But has now become its own program. I do not know if YubiKeys will work with it.