As far as I can recall.. the seal only subdues their free will, and has no bearing on whether they are alive or not. The IWR simply revives them, and the fuda tag restrains their mentality. Orochimaru's fully restrained the mind to his will, robbing them of their free-will. Kabuto's doesn't fully taking away their free-will, instead.. it allows him to temporarily control them when he needs to (I believe)
And there's no telling whether killing the summoner ends the summons or not. Don't know yet. Only thing known so far is that the summons themselves can't be killed conventionally.