I've changed my mind. :)

>>>>> In <yotlr8gqqapy.fsf@jpl.org>
>>>>>	Katsumi Yamaoka <yamaoka@jpl.org> wrote:

> Well, there is a non-Gnus frame on the display A, and there is
> an iconified Gnus frame on the display B.  If a user clicks the
> news toolbar (or types M-x gnus-other-frame) on the display A, a
> Gnus frame will be popped up on the display B.  I think it is a
> correct behavior.

No, it's not correct.  That behavior is quite inconvenient if
the display B is away from the display A.  Here's a new one.
Jinhyok, could you please check it whether you are pleased?