Proof using.
intros P s alP.
case (classic ((eventually (~_ P)) s)); trivial.
intros evP.
apply not_eventually_not_always in evP.
contradict alP.
assumption.
Qed.

Lemma not_until_release :
forall (J P : infseq T -> Prop) (s : infseq T),
~ until (~_ J) (~_ P) s -> release J P s.