Okay, define "closed" for me.

To my knowledge, there are two related definitions of closed vs. open architectures in computing.

One has to do with hardware. I think we can all agree that no cellphone is open architecture. I don't think this is necessarily by design, but is a consequence of miniaturization. Regardless, that's clearly not what we're talking about anyway.

The other is software related. It was popularized in the 80s when Unix vendors were trying to get people to move away from mainframes, the idea being that if you invested in mainframe software development, that software would take a huge amount of effort to run under any other system, effectively locking you in to their platform, whereas Unix had universal APIs (open standards) so that if you wanted to change hardware vendors, you didn't have unrecoupable development costs with the old system.

If you want to develop for the iPhone, your only target is the iPhone. There are no other even vaguely compatible vendors. If you develop for Flash, there are potentially many compatible hardware vendors. In addition, Apple has decided to contractually prevent you from using any technology that would allow you to be able to recoup your development costs. Their intention is for you to find it to be too much effort to develop for a second platform. It's vendor lock-in, very straightforwardly, and is exactly what the term "open systems" was popularized to be in opposition to.

That said, using Flash also locks you into using Flash, where there are no other (virtual) hardware vendors, though they have relaxed their licensing to allow there to be other hardware vendors. (Maybe that was always the case; I'm not sure.) So I'm not saying that Flash is really any better. Java would make more sense, since it actually is an open standard, but that's neither here nor there, since Apple's license precludes Java, too.