In the wake of Apple’s new in-app subscription rules, we’ve already seen revolt from the makers of Readability and TinyGrab, who sent out blistering open letters yesterday explaining how Apple’s new rules effectively barred them from the App Store.

TinyGrab’s take was particularly interesting: the new in-app subscription rules prevent software-as-a-service apps (like Evernote, Dropbox, TinyGrab and more) from coming to the App Store at all. But in a recent email from Steve, the on-leave Apple CEO says that that’s not the intention at all…

A MacRumors reader wrote Steve over the weekend, asking whether or not the new App Store guidelines would prohibit SaaS companies from doing business on the App Store.

Always succinct, Steve wrote back:

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

In this view, an app like Readability breaks the rules, but an app like TinyGrab, Evernote or Dropbox has nothing to fear… for now.

It’s still not heartening news, though. It’s a gentleman’s agreement from a company with a history of breaking them (the “new” in-app subscription rules have always technically been extant, but they were only recently enforced). If SaaS services don’t fall afoul of the guidelines, Apple needs to revise the guidelines to say as much.

Apple’s new in-app subscription rules seem pretty clearly aimed at driving competitors of either current services (like iBookstore/Amazon) or future services (like iTunes in the cloud/Rhapsody/Last.fm/Spotify) out of the App Store. Apple may not be gunning for the likes of Dropbox or Evernote now… but that could swiftly change, as it has now for iOS publishers.