csekorajmund@gmail.com:
It becomes seki or a ko if black plays the bent 4. Since we have no information about anything else on the board (ko threats) it doesn't make sense to call it a kill, especially when the title says "no ko" and the ko is the very requirement for the kill...

Paiguru:
"No Ko" is misleading. Only dead in Japanese ruleset.

TherapieGo:
"Bent four" in the corner is dead – if there are no unremovable ko threats. If there is a seki on the goban then the "Bent four" becomes a simple ko.

kgcsabi:
According to the linked page: Bent four in the corner is dead – if there are no unremovable ko threats. This puzzle requires a solution that does not involve ko at all.

LastDreamer:
It is not possible to kill the group unconditionally. Only ko or seki. Bent four it is a ko in this case

Girod:
i think it's always ko or seki ?