For MPK part, is it considered MPK if a player jumps into Ozma's zone, and then another jumps in and attacks the boss and both get killed? As far as I know, that's not considered MPK since they both are in the boss zone already, and the boss will automatically add any player there to their aggro list. MPK as I know it, is when you drag a mob and use it's AOE to kill another player that did not engage the mob nor was on its aggro list.
What I saw in the screenshots was that one of the player's friends was dead with two others in Ozma's zone. And knowing Ozma, there have been many cases where players by accident aggroed him. And it could be one of those cases also. If it was intentional, is it a rude move? yes, but it's still not against TOS as far as I know, since they all jumped willingly into the boss zone. Just as sniping a portal is rude if you know someone was waiting hours for that, but it's still not against TOS.