In a follow-up to yesterday’s Readability news, MacRumors reports an iOS developer emailed Steve Jobs with his concerns about the new restrictions on “Apps offering subscriptions.” Jobs reportedly replied, in his trademark laconic style. (“SaaS” is the abbreviation for “Software as a Service”, the term for the type of service Readability offers.)

We created subscriptions for publishing apps, not SaaS apps.
Sent from my iPhone

It is unclear what this means for Readability, however. The lines are a bit blurry, given that Readability’s app, as John Gruber points out, involves “serving up content” exactly the way a magazine app might.

Erick Schonfeld at TechCrunch asks the question that logically follows: “What’s a publishing app?” If Readability qualifies, so too might other news reader apps that charge a subscription.

But what is a news publishing app? They are clearly news-reading software. And what if Twitter or a Twitter client started charging subscriptions? Are those publishing apps or a communications apps? Just think about Flipboard or Pulse, which transform Twitter and other feeds into a dynamic, realtime, personalized publication. If those apps started charging subscriptions (both are currently free), I bet they would have to go through Apple’s subscription system just like Readability.

And what about other media apps like music or movies? Pandora and Netflix have been two of the big names brought up as concerns, but given that Amazon just launched movie streaming for paid Prime subscribers, it could be affected by this too. And personal publishing apps such as Evernote?

Michael W. Perry made a good point in a comment on the Readabiity story. He wrote that anti-trust might not be the only thing Apple’s policy change lets it in for:

The real issue is false advertising. Apple’s ads have trumpeted all the apps that run freely on their iDevices (the bait). Yanking some of them, particular [sic] popular ones such as the Kindle, would constitute bait-and-switch, particularly since Apple’s goal is obviously to drive readers to the iBookstore (the switch). Not only could the feds and the states get involved in that, there could be class action lawsuits–perhaps all at once.

It will be interesting to see how this all shakes out.