I wrote last week that The Wall Street Journal was screwing up by not charging for its swell new iPhone application and its somewhat-older BlackBerry one, despite charging good money for its website and for a paper subscription.

Amy Gahran, whose Poynter post inspired mine, wrote in comments that “the WSJ may be exploring the value of free content, without actually saying so.

I hypothesized that Dow Jones might be trying to introduce the apps to a wider user base to hook them before introducing charges.

But I’m told by a Dow Joneser familiar with the matter that the reason the Journal isn’t charging for the app is simple: It can’t. The technological platform to do so isn’t up to speed yet.

This person says Rupert Murdoch himself said he was “displeased” that his company’s valuable content is being given away free on the iPhone and BlackBerry and that his displeasure has been made clear more than once to those responsible for mobile.

Dow Jones did not respond to repeated requests for comment.

The platform to charge won’t be ready until early fall, by which time the Journal app’s user base will have gotten good and used to getting it for free. Meanwhile, any potential incremental revenue from mobile subscriptions is being left on the table. It’s probably not much, but hey—anything helps right now!

I’d be happier if this is indeed just a snafu and not an intentional strategy. Giving it away free would undermine the incentive to pay for the website (now going for $149 a year) or for the newspaper (which brings in the vast majority of revenue through advertising).

And as has become abundantly clear: Online ads just aren’t going to pay for the quantity or quality of journalism we need.